Tuesday, June 29, 2010

Revolver: Colt Single Action Army a.k.a. The Peacemaker

In the last post, we saw the history of the first Colt six-shooter, the Walker Colt model, followed by the Colt Dragoon family and the rise of machine-made interchangeable parts and innovations in machining technology.

Colt went on to make a lot of weapons during the civil war, such as the Colt Navy 1851 pistol and Navy 1861 models. Some of the famous users of the 1851 Navy model included Wild Bill Hickok, Doc Holliday, Sir Richard Burton, Ned Kelly and General Robert E. Lee. These models sold very well and made the Colt company a lot of money.

However, it must be noted that the Colt revolvers were still using percussion cap technology well into the 1860s, even though metal cartridge technology and the center-fire cartridge has already been invented. The reason for this is because Smith & Wesson held the patent for bored through revolver cylinders and Colt didn't want to pay royalties. So Colt elected to wait until 1869, when the patent ran out, before they started work on a new revolver. This revolver competed successfully in the US Army trials of 1873 and was adopted as the new standard military revolver. It remained as the official service revolver until 1892 and has continued to be manufactured all the way to the present day. The Colt Single Action Army Revolver was nicknamed the "Peacemaker" and the "Equalizer" (because it made all men equal!) and it was known as the "gun that won the west".

Public domain image from wikipedia.com. Click to enlarge.

The picture above shows a Colt Peacemaker made in 1956 (the "second generation" model!). The Colt Peacemaker is a classic weapon seen in many western movies. It was the weapon of choice for Wyatt Earp, Bat Masterson, General George S. Patton and Lawrence of Arabia. In fact, Lawrence of Arabia considered it his lucky weapon because he was once attacked by an Arab bandit in pre WW-I Mesopotamia. The bandit seized Lawrence's revolver and was threatening to shoot him with it, but could not do so because he did not understand its mechanism. Since then, Lawrence always carried one for good luck.

Like the previous Colt models before it, this is also a single action revolver. However, it uses a centerfire cartridge instead of percussion caps and black powder. Loading is accomplished by opening a loading gate on the side and dropping cartridges, one at a time into the revolver. Although six cartridges can be loaded into it, most people load five chambers and leave the chamber which is facing the hammer empty as a safety precaution. This way, the weapon cannot fire if it is dropped accidentally. To fire, the user simply pulls the hammer back, which cocks the hammer back and also rotates the cylinder to the next chamber. Then the user pulls the trigger to fire the weapon. The user can also fire rapidly by holding down the trigger with one hand and repeatedly pulling the hammer back with the other palm in a fanning motion. While this is not considered a safe way to fire, it is the image of a gunfighter thanks to Hollywood movies.

The Colt Peacemaker was originally manufactured to fire a .45 caliber Colt cartridge for the army and it was initially priced at the low cost of $17. Various civilian versions were soon manufactured in other calibers as well. For instance, the Colt Frontier models were designed to use the Winchester .44-40 and .32-20 cartridges because many western frontiersmen, cowboys and lawmen owned a rifle as well as a revolver. Since Winchester rifles were commonly used at this time, Colt designed the revolver to use the same cartridges as the rifles, so that the user only needed to carry around one type of ammunition. It was also certified in the 1900s to use the new smokeless powders instead of black-powder. Other popular calibers followed in the 1900s as well, including the .357 magnum, .38 special etc.

The first generation of the Peacemaker was made between 1870 and 1941, in a variety of calibers from .22 rimfire to .476 Eley cartridge, totalling about 30 separate calibers, which gives a measure of this weapon's popularity. There were approximately 357,000 first-generation revolvers of this model made. The second generation model, like the one pictured above, was made between 1956 and 1974 and about 73,000 were made. In 1976, the third generation was issued and this one featured a different thread pitch in the rifling of the barrel and a redesigned cylinder bushing. The third generation model was made until 1982 and 20,000 were made. In 1994, production of the third generation model restarted (sometimes called the fourth generation) in a number of popular calibers.

Colt still makes this weapon and lists it in its catalog, as do a host of other manufacturers who also make near copies of it. This weapon was the inspiration for a number of other modern revolvers and is truly "the gun that won the west."

Sunday, June 27, 2010

Revolver: Walker Colt & Colt Dragoon Revolvers

In our last post, we discussed the Paterson Colt, which was the first weapon to bear the term "revolver". As we noted in our previous post, the model was a failure in most places, except in the Republic of Texas, where they bought up enough models in .36 caliber that the .36 caliber version began to be called the "Texas Paterson." Many of the users of Paterson Colt models were members of the Texas Rangers.

Captain Samuel Walker of the Texas Rangers, was one of the officers that was highly impressed by the Colt weapons, but he wanted a few improvements made to it. In 1846, he collaborated with Samuel Colt to make a new weapon for use with the Rangers. At that time, the Texas Rangers were using a single shot close range pistol made by Aston Johnson which could be put in a holster on the saddle. What Walker wanted was a new handgun that was extremely powerful at close range and could be carried in a saddle holster like the pistol. However, this weapon would have to be a revolver to allow the rider to fire multiple shots without reloading. He persuaded Samuel Colt to increase the caliber of the weapon from .36 to .44 or .45, so that it could not only be used to kill enemies, but also the horses that they were riding on. The newly designed weapon was called the "Walker Colt" in honor of Captain Walker.

Public domain image from wikipedia.com. Click to enlarge

The new revolver was designed to fire a .454 inch (11.5 mm.) diameter bullet. The Walker Colt retained the single-action design of the Paterson Colt, along with the hinged loading lever and capping window design of the 1839 model Paterson Colt. Unlike the Paterson Colt though, this weapon could carry six bullets at one time. This meant that the Walker Colt was the original "six-shooter". Also, this weapon had a fixed trigger and a trigger guard unlike the Paterson colt which had a folding trigger that would drop only when the hammer was cocked and no trigger guard.

The weapon was heavy (2 kg. when empty) for a handgun, as it was meant to be carried in a saddle holster. It was also more powerful than any other handgun then in existence, since it used almost twice the gunpowder charge of any handgun in each of its chambers. Matter of fact, the standard amount of gunpowder used per chamber was 3.9 gm. which was about the same used in some muskets! Despite the fact that it used black-powder for its gunpowder, the Walker Colt was the most powerful handgun in existence between 1847 and the 1935, when the first .357 magnum was introduced. Walker wrote that this gun was "as effective as a rifle at 100 yards and superior to a musket at 200 yards." In practice, it was more useful at a range of 50-100 yards.

The original order of the Walker Colt models from Texas asked for 1000 of them to be delivered, along with accessories. At this point though, Samuel Colt was without a factory, due to the failure of the earlier Paterson Colt model and the Patent Arms Manufacturing Company being taken over by his creditors. Hence, he subcontracted the actual manufacture of these weapons to Eli Whitney Blake who had a gun factory in Whitneyville, Connecticut. Eli Whitney Blake was the nephew of the senior Eli Whitney, the inventor of the cotton gin. Eli Whitney Sr. was not only the inventor of the cotton gin, he'd also invented an early milling machine. He was a pioneer in adopting power tools for manufacturing, invented the modern assembly line and promoted the concept of interchangeable parts. His talented nephew, Eli Whitney Blake, helped him build the gun factory at Whitneyville and took over after he'd passed away. Samuel Colt asked Eli Whitney Blake to build him 1100 revolvers, 1000 for the Texas order and 100 to be used for private sale and promotional gifts. The ordered revolvers were shipped out in mid-1847. These original 1100 models are now extremely rare and worth at least $150,000 each, with one going on sale in 2008 for $920,000.

Due to the huge success of the Whitneyville built Walker Colts, the Colt reputation was made and it enabled him to later build his own Colt factory. Sadly, Captain Walker, after whom the weapon was named, was killed in action in October 1847 and legend has it that at the time of his death, he was carrying two Walker Colt models presented to him by Samuel Colt, which had only arrived a few days before. Nevertheless, the huge success of this weapon in the hands of the Texas Rangers was noticed by the United States government and Colt was given an order to deliver more weapons to the United States Mounted Militia (Dragoons), based on the Walker Colt model.

Some of the problems of the early Walker Colt models included a tendency for the cylinders to rupture due to too much gunpowder being loaded into them and also primitive metallurgical techniques of that time. Another problem was an inadequate catch for the loading lever which would cause it to fall out due to the firing recoil and interfere with the action of the weapon. Some of the users of the Walker Colt fixed this loading lever issue by binding the lever to the barrel with a leather band.

The Colt Model 1848 Percussion Army Revolver fixed these issues by making a smaller chamber that allowed about 15% less gunpowder (3.25 gm. instead of 3.9 gm.) to reduce the problem of ruptured cylinders. The falling catch problem was solved by redesigning the catch to hold the loading lever even with heavy recoil. The size of the barrel was also reduced from 9 inches to about 7.5 inches to make the weapon slightly lighter and more manageable. Since this weapon was originally ordered for the United States Mounted Militia (known as "Dragoons"), this model was called the Colt Dragoon. This new weapon was a huge success among civilians as well and Colt produced three separate variations of these weapons between 1848 and 1860.

GFDL licensed image from wikipedia.com. Click to enlarge.

The above image is of a Colt Dragoon third variant model. The three variants can be told apart mainly by the shape of the trigger guard (squared edges in the first two variants and rounded edges in the third variant) and the shape of the cylinder notches (oval in the first variant, rectangular in the other two variants). The third model variant also has some instances with different sights and provisions to attach a shoulder stock.

Other variations included a smaller version called the 1849 Baby Dragoon and the 1851 Pocket Navy and Pocket Police versions. The Baby Dragoon was marketed to civilians and was extremely popular during the California Gold Rush.

Almost 20,000 of these weapons were produced for sale in the United States and an additional 750 were produced for the British market between 1848 and 1860 before the Colt Dragoon was replaced by the Colt Model 1860. Colt Dragoons are still being sought by collectors today and an original model still fetches high prices.

Due to the success of his weapons, Colt managed to build his own factory in 1851 in England, the first American manufacturer to do so. In 1855, he opened a new factory in Hartford Connecticut, which incorporated the latest technologies at that time and was capable of building 5000 handguns in its first year of production. Knowledgeable in the advances in machining technology and interchangeable parts, about 80% of his parts were made by the most up-to-date precision machinery of the mid 19th century. By 1856, the factory was producing 150 weapons a day and the reputation of Colt for accuracy, reliability and workmanship quality had spread throughout the world.

It must be mentioned also that a large part of Colt's success in machining technology was due to the efforts of an extraordinary individual. Around 1849, when Samuel Colt was building his new factory in Connecticut, he managed to lure away a mechanic by the name of Elisha K. Root from the Collins company, which made axe-heads. Elisha Root already had a name as a mechanic and inventor and was making machines to manufacture axe-heads more efficiently, when Samuel Colt lured him away, by taking the simple route of paying him twice what Collins was paying him at that time, and making his supervisor of Colt's new factory. Mr. Root set about changing the way that Colt manufactured firearms by building about 400 machines (state-of-the art drop hammers, boring machines, jigs and fixtures etc.) to make interchangeable parts, that made the Colt factory the leading model of efficiency in the world. It was when working at Colt that he invented a new Universal Milling Machine. This milling machine was manufactured for Colt by a subcontractor called the Lincoln Iron Works and later became called the "Lincoln Miller". About 150,000 of these machines were sold by the 1890s and it became the most common machine tool in America and made the United States the world leader in the design and production of machine tools. Elisha Root also attracted many other star employees to work for Colt. When Samuel Colt died in 1862, Elisha Root took over as the president of the Colt company.

Due to the amount of research into machining technology, the area around the Colt factory became a hot-bed for mechanical innovation (sort of a Silicon Valley of its time). For example, one employee at Colt's plant was William Mason, who secured 125 patents for machinery that made guns, power looms and steam pumps. Yet another inventor in Colt's factory was Christopher M. Spencer, who invented the world's first automatic turret lathe. Another Colt employee was Charles E. Billings, who invented the drop hammer used for metal forgings. Charles Billings also invented the copper commutator, a key piece of technology for electric motors and generators. Two other employees were Francis A. Pratt and Amos Whitney, who improved the Lincoln miller, invented a thread boring machine and later went on to found Pratt & Whitney. Simon Fairman invented the chuck that holds the workpiece on a lathe and his son-in-law, Austin F. Cushman invented the first self-centering chuck called the Cushman Universal Chuck.

Copies of the Walker Colt and the Colt Dragoon are still being made today, especially by the Uberti company of Brescia, Italy.

Revolvers: Colt Paterson

After our discussions about early proto-revolvers such as pepper-boxes, it is time to start talking about true revolvers. In fact, we will start off with a discussion on the weapon that was the first to be described with the term "revolver". This honor belongs to the Colt Paterson revolver invented by Samuel Colt in 1836. The name "Paterson" comes from the fact that the factory that produced this weapon was located in Paterson, New Jersey.

Company lore has it that Samuel Colt originally got the idea for its mechanism during a sailing trip between Boston and Calcutta aboard the brig Corvo in 1830. He observed the ratchet-and-pawl mechanism used by the ship's steering wheel and noted how each spoke in the steering wheel came in contact with a clutch that could hold it in place if needed. He was inspired enough to carve a wooden model of a revolver on this voyage. A few years later, he applied for patents in the US, England and France and received his patents in 1836. He then built the Patent Arms Manufacturing Company in Paterson, New Jersey, to manufacture this weapon.

The Paterson revolver was the first repeating firearm that consisted of a revolving cylinder with multiple chambers that aligned to a stationary barrel. Until then, repeating firearms had multiple barrels. This revolver was a 5-shot model with a single action mechanism using percussion cap technology. A single-action mechanism means the user has to manually pull back the hammer to cock it. The act of pulling the hammer back also rotates the cylinder to bring the next chamber in line with the barrel and also locks it in place. When the user pulls the trigger, the hammer is released and strikes the percussion cap of the chamber that happens to be on top of the weapon, thereby discharging it.

Public domain image from wikipedia.com (click to enlarge)

The above picture contains two models of Paterson Colts. The smaller model is an original model from 1836 and the two crossed revolvers are the 1839 models. The astute reader might note that the triggers appear to be missing on the two crossed revolvers and that none of the revolvers have a trigger guard. This is in fact a feature of the Paterson Colt models. The trigger is actually a folding one. When the user pulls the hammer back, not only does the cylinder rotate, but the trigger also drops out of the frame in firing position. This is why there is no trigger guard.

The astute reader may also have noted that the 1839 models have a lever under the barrel that the 1836 model doesn't have. We will study what that lever does in a little bit. First, let us understand how to reload the 1836 model revolver which will go into explaining the strange lever. The 1836 model revolver had a somewhat cumbersome reloading procedure that required the user to disassemble the gun. The procedure went as follows:
  1. Put the hammer at half-cock. This frees up the cylinder and allows it to be removed.
  2. Push the barrel wedge which is under the barrel and holding it in place.
  3. Now pull the barrel and cylinder from the revolver's frame.
  4. Load each of the chambers of the cylinder with enough gunpowder, leaving enough room to seat a lead ball into each chamber
  5. Push a lead ball into each chamber with a special ramrod tool. This took a bit of effort in the early models.
  6. Push the cylinder and barrel back into the revolver's frame and push the barrel wedge back into place.
  7. Place percussion caps on each of the nipples around the cylinder using the special Colt capping tool that comes with the revolver.
Since Colt often supplied spare cylinders with the revolver, many people would walk around carrying loaded and capped spare cylinders in their pockets for faster reloading. That way they could quickly pull out the barrel and cylinder, pull a fully loaded new cylinder from their pocket and put the revolver back together and ready to go. This practice was not very safe in case the loaded cylinders were accidentally dropped.

With a view to improving the loading time, Colt improved the model and the 1839 models featured an integrated loading lever and capping window. As the reader may have noted in the picture above, the 1839 models have a feature that the 1836 model doesn't have. Under the barrel is a hinged ramrod lever that is missing in the 1836 model. This way, the user could not lose the ramrod and ramming the lead balls into the chamber also became easier. Therefore, the 1839 model did not require the user to disassemble the weapon for reloading. This hinged loading rod feature was an innovation that was widely copied in future revolvers as well.

The Paterson revolver was sold with different barrel lengths from 2.5 inches to 12 inches long, with 7.5 and 9 inch barrels being the most common. The barrels were all rifled, so as to improve accuracy. Calibers varied from the original .28 caliber to the .31, .34 and the very popular .36 caliber. The barrels have a small projecting blade sight in front and the rear sight is a notch cut into the hammer lever, which aligns with the front sight when the hammer is cocked.

Despite being an innovative weapon, the Paterson revolver was not a success. It was expensive for its time, costing around $40-50 per piece. Colt managed to sell a few to the United States Army and they saw limited use, but the US Army considered them too fragile and prone to malfunctioning. However, the Republic of Texas (which was still not a part of the United States then) bought a number of them for their army and navy. The Texas Rangers found these weapons especially useful against the Comanche tribes and some of their key commanders such as Colonel Jack Hayes and Captain Samuel Walker began to push for military contracts to acquire more of them, especially in .36 caliber. This associated the name "Texas Paterson" to the .36 caliber model of these revolvers.

Due to the commercial failure of the Paterson revolver, the Patent Arms Manufacturing Company was forced to stop manufacturing in 1842. A creditor named John Ehler then acquired the factory and continued manufacture until 1847, when he was forced to close it down as well. However, the design was influential and innovative enough that its ideas were used in future models as well. Captain Walker, in particular, thought that the Paterson could be improved and therefore submitted several design improvement ideas to Colt. Therefore, when Colt opened a new factory in 1846, the new model was called the Walker Colt revolver. We will study the Walker Colt in the next post.

Revolvers: Pepper-Box Revolver

The first repeating revolver type weapons and predecessors of modern revolvers are called pepper-box revolvers. The name has to do with the fact that they tend to resemble an old-fashioned pepper mill.

The chief characteristic of pepper-box revolvers are that they have multiple barrels that revolve about a central axis.

The firing mechanism can be practically any firing mechanism that has been used in the history of firearms. Indeed, there are pepper boxes that utilize matchlock, wheel lock, flintlock, percussion cap, pinfire cartridge, rimfire cartridge or centerfire cartridge.

The first pepper-box revolvers originated in the 1500s and used matchlock mechanisms. The user would pre-load all the barrels ahead of time and then apply a match to fire each one in turn. By the 1790s, the firing mechanism of choice was the flintlock and Nock's of England was well known for making pepper-box revolvers using a flintlock mechanism. All these early pepper-box revolvers had no automated mechanism to rotate the barrels, so the user had to do this manually after each shot.

The above is a fine example of a pepper-box revolver using a flintlock firing mechanism. Each time the user wants to fire it, he or she would have to turn the barrel, then open the pan and put some priming powder in, then cock the lock and then pull the trigger to fire. The weapon fires the barrel that happens to be at the top-most position when the trigger is pulled. The advantage of this over a single barrel pistol is that the user saves the time of loading a new ball and powder each time, as this can be done in advance for the six barrels.

Later on, when percussion cap technology was invented, the industrial revolution was in full swing and this enabled pepper-box revolvers to be mass produced. This made these revolvers much cheaper and thus affordable to a lot more people.

The image above is a 24-barrel pepper-box revolver using percussion cap technology. This particular specimen was made in the 1850s by a Belgian gun maker called Mariette. The user would load each barrel individually and then put a percussion cap on each of the nipples sticking out at the back of each barrel. While a 24-barrel specimen like this would take at least 40-60 minutes to load, but only take a short time to fire.

With the advent of pinfire cartridges, the pepper-box regained some popularity in the late 1800s as a small concealable weapon.

Public domain image from wikipedia.com

In the above example, we see a French-made Lefaucheux pepper-box revolver using pinfire cartridge technology. The user first removes the cylinder from the weapon by unscrewing the nut marked in the figure. The user then loads pinfire cartridges into the back of the cylinder, making sure that the firing pins of the cartridges stick out of the holes in the cylinder. The user then pushes the cylinder back into the weapon frame and screws the nut back in place. When the user pulls the trigger, the hammer strikes the pin of the cartridge on top of the weapon and it fires.

Most pepper-box revolvers are short range weapons and therefore, many specimens have no rifling at all, since it is not necessary for such short ranges. There are some examples with rifling in the barrels, but the majority of them have no rifling, including many that were manufactured decades after it became common to add rifling to other types of weapons.

One of the difficulties with pepper-box pistols is adding sights to the weapon, but since the weapon is usually designed for point-blank range use, this is not much of an issue. It is also difficult to maintain the balance of such a weapon.

Pepper-box revolvers started to disappear from public view around the 1840s or so, after the invention of true revolvers by Samuel Colt and others. However, there are still a few pepper-box type revolvers still being used today, most notably a P11 underwater revolver designed by Germany's Heckler & Koch.

The idea of a multiple barrel weapon has also been used in non-portable weapons. Richard Gatling used the idea his Gatling gun, which was mounted on a cart. The modern descendants of the Gatling gun are still used to this day, notably by the Fairchild Republic A-10 Warthog and the Lockheed AC-130 airplanes.

Saturday, June 26, 2010

Revolvers: Basics

A revolver is a weapon that allows the user to fire multiple times without stopping to reload. While there are some other weapons, such as double barrel shotguns, that also allow a user to fire more than once, a characteristic of revolvers is that the firing chambers of a revolver turn about an axis (i.e. they "revolve") and this is the origin of the name.

Early revolvers were called pepper-boxes and they had multiple barrels which revolved about an axis and a common firing mechanism. The earliest ones exist from 1597 (a revolving arquebus) and use matchlock mechanisms. In the 1700s, James Puckle invented the "Puckle Gun" which had multiple firing chambers and one common barrel and firing mechanism. A hand crank rotated the firing chambers and brought each one in line with the barrel and firing mechanism. Elisha Collier of Boston, patented a popular revolver model in 1818, which used the flintlock firing mechanism. He also produced revolving shotguns and rifles. In 1819, John Evans of London bought Collier's patent and produced several weapons which were used by British soldiers stationed in India.

Many big developments in revolver technology were by Samuel Colt. In 1836, he patented his first revolver model. It was manufactured in Colt's factory in Paterson, New Jersey, and hence it is popularly called the "Paterson revolver." While Colt's name is the most famous one associated with revolvers, he never claimed to invent the concept. In fact, the Paterson revolver was an improved variant of the concept invented by Collier. Some of Colt's big innovations dealt with applying concepts of mass production, interchangeable parts and assembly line techniques to revolver production and this reduced the price of revolvers. He was also an excellent salesman and promoter and his weapons became extremely popular with the public. One of his later models was nicknamed "Peacemaker" and "Equalizer". A popular saying of the time went "Abe Lincoln may have freed all men, but Sam Colt made them all equal!"

Colt's first revolvers all used a ratchet and pawl mechanism to hold the cylinders in place. They were also "single action" mechanisms, i.e. the user must cock the weapon manually. The act of pulling back the hammer to cock the weapon also rotates the cylinder. Once the weapon is cocked, the user can pull the trigger to fire it.

Later on in 1851, a British gunsmith named Robert Adams invented the first "double action" revolver. In this mechanism, pulling the trigger halfway automatically rotates the cylinder and cocks the hammer. Pulling the trigger back some more releases the cocked hammer. Thus, the user can fire the weapon with just one trigger pull. The Adams revolver was hand-crafted, which made it more expensive than Colt's design. It also had a few flaws in the hammer and frame. This could only fire in double-action mode and was hence called a "DAO revolver" (i.e.) Double-Action Only. Improvements to the Adams model were made by Lieutenant Frederick E.B. Beaumont, a veteran of the Crimean war and the resulting model was called the Beaumont-Adams revolver. This new model could be operated in both single-action or double-action mode and was such a huge success that Samuel Colt had to shut down their factory in England as a result. Mechanisms that operate in both single and double-action mode are called DA revolvers (DA standing for "Double Action").

Most modern revolvers to this day are double-action. They are still used by law-enforcement around the world and remain popular among many private gun-owners. In fact, it is said by many that the best way to teach a new handgun enthusiast about shooting basics is to start with a revolver first.

Some of the advantages of revolvers over other multiple firing mechanisms (notably the automatic pistol) are:
  1. Simpler mechanism, which is less prone to jamming.
  2. Ease of use: With a double action revolver, all one has to do is pull the trigger. With a single-action revolver, one cocks the hammer and then pulls the trigger. Unlike a pistol or an automatic rifle, there are no additional safety mechanisms that need to be meddled with.
  3. More powerful cartridges can be used: Due to the robust design of the revolver, bigger magnum cartridges can be used with one. In fact, the biggest handgun cartridges are mostly designed for revolvers.
  4. Much easier and faster to reload than a pistol. Anyone who has loaded a pistol or rifle magazine knows that the first few cartridges go in easy, but the last 3 or 4 cartridges take considerable effort to push into the magazine. With a revolver, one merely opens the chamber and drops cartridges into it.
  5. Works with greater range of ammunition types: Revolvers can be used with blanks, wad-cutters etc., which do not work with automatic pistols.
  6. Easier cleaning and maintenance: Since revolvers have fewer moving parts than automatic pistols and rifles, they don't require disassembly and are therefore much easier to clean and maintain.
On the other hand, pistols generally hold more ammunition, are lighter and slimmer profile, and also use cheaper ammunition than revolvers.

One of the reasons that revolvers are/were popular with Indian police has to do with poor quality of ammunition available to them. If a pistol misfires due to faulty ammunition, the user has to pull back the slide and extract the faulty cartridge before it can be fired again. This takes a bit of time to accomplish. With a revolver, if one cartridge is faulty and does not fire, the user can simply pull the trigger again and the cylinder automatically rotates and brings up the next round ready to fire.

In the next few posts, we will look into various types of revolvers.

Thursday, June 24, 2010

Bullets: Modern Bullets - II

In our last post, we looked at advances in bullet technology from the 1900s onwards. We also studied some modern bullet types. Now we will study some more modern bullet types.

The first type of modern bullet we will study is the "boat-tail" bullet. This type was invented in 1898 in France, as an improved spitzer type bullet (which we studied in the last section). The problem was that as bullets speeds started to increase, it was found that as a bullet moves in the air, the resulting vacuum created by its motion slows down the tail end of the bullet. It was found that by tapering the back of the bullet, the drag caused by the vacuum was very much reduced. The improved bullet was called Balle D by the French and the design was soon copied by other countries.

Note the typical taper at the back of the bullet that characterizes a boat-tail bullet. Above 400 yards or so, boat tail bullets come on their own and show much more improved performance over normal spitzer bullets. Many high powered bullets these days are boat-tails.

The next type of bullet we will study is the tracer bullet. These bullets were originally introduced by the British for use with the venerable .303 rifle in 1915. The base of a bullet of this type is hollow and contains some pyrotechnic material, such as phosphorus, strontium compounds, barium compounds, magnesium etc. When the bullet is fired, these compounds ignite and leave a visible trail along the path of the bullet. This allows the shooter to see where the bullets are ending up. Since the tracer chemicals burn as the bullet flies in the air, the bullet loses mass as it travels. Hence, a tracer bullet must be spun at a higher rate of spin than a normal bullet in order to maintain stability in the air. Also because of the loss of mass, the tracer bullet often hits at a somewhat different location from where a normal bullet would go.

There are a few types of tracer ammunition. The oldest type is the bright tracer, which starts burning the moment the bullet leaves the barrel, and burns very brightly. However, this trail is visible to everyone around and thus gives away the position of the shooter as well. These types also tend to overwhelm night vision devices with their bright glow. Newer types of tracers attempt to fix this issue. Subdued tracers have a delayed startup and only burn brightly after the bullet has traveled past about 100 meters or so. This way, it does not give away the shooter's position. Yet another type of tracer bullet called the "Dim Tracer" does not produce much of a trail since it mostly emits infrared light. It is intended to be used along with night vision equipment. Another new development in tracer technology uses an LED instead of chemicals, so it is only visible from the position of the shooter. This also has the advantage that the tracer does not lose mass as it travels and hence stays more accurate. US forces generally tend to load their ammunition so that every 5th bullet is a tracer bullet.

The next bullet type is the armor piercing type. Basically, this looks similar to the jacketed bullets we studied in the previous post, but the tip is made of a harder material such as tungsten carbide, steel, depleted uranium etc.

Another type of bullet is the flechette bullet. Basically these bullets have vanes in the back, similar to feathers at the back of an arrow. These vanes serve to keep the bullet steady in the air, so there is no need to spin the bullet with rifling. Some shotguns firing flechette bullets were introduced in Vietnam and there is still research this field today.

Tuesday, June 22, 2010

Bullets: Modern Bullets - I

In our last post, we saw how spherical balls were gradually starting to be replaced by elongated bullets, especially since it was determined that elongated bullets could be given more accuracy than spherical bullets, if they were spun about their axis by rifling. Now we will study the development of modern bullets.

Recall that in our discussion about the early bullets, we noted that they were mainly made out of pure lead because the material is easy to shape, cheap, readily available and extremely dense. The problem with lead is that it is also very soft and melts easily. Lead balls performed satisfactorily for a few centuries when gunpowder was low quality and velocities of the bullet were not that high. However, as the gunpowder quality and power began to improve and as the bullets began to fit the gun barrel more tightly, the velocity of the bullet began to increase and the pressure and temperature in the barrel was also higher. The temperature of the bullet would rise not only because of the hotter burning gunpowder, but also due to the friction generated by rubbing against the barrel. This meant that the lead bullet had a good chance to melt and deform due to the extra temperature and pressure. This would cause the bullet to leave a good bit of lead behind inside the barrel and it would have to be cleaned often. The deformation of the bullet would also cause a loss of accuracy.

One solution that we've already seen when discussing the manufacture of shotgun pellets earlier, is to add a bit of antimony to the lead. This increases the hardness of the lead alloy and makes it resist higher pressures.

However, adding antimony did not solve matters much, especially after more powerful gunpowders such as cordite came out. The bullet would be stripped due to the rifling and the lead would deposit on the inside of the grooves, making the weapon useless very quickly.

The next solution was invented by Lt. Colonel Eduard Rubin at the Swiss Federal Ammunition Factory and Research Center in Thun, Switzerland in 1889. His solution was to make a thin outer layer of copper which would be filled on the inside with lead. Since copper melts at a higher temperature than lead, is harder than pure lead and has a specific heat capacity higher than lead, the outer layer prevents the bullet from getting deformed too much. The inner layer of lead adds to the weight of the bullet. Such a bullet is called a jacketed bullet. The jacket may extend throughout the front and sides of the bullet, in which case it is called a full-metal jacket (FMJ), or it may only extend around the parts that fit tightly around the barrel and the tip may be of softer material, in which case it is called a soft-point bullet.

Note that the jacket is not always made of copper these days. Cupro-nickel and other copper alloys, steel and gilding metal are all commonly used these days. Nylon and other synthetic materials were also tried out without much success.

Note that a pure lead bullet expands on striking the target because the lead in the back mushes the lead at the front of the bullet and thereby causes much more damage to the target after it expands. A full-metal jacket bullet does not expand much on striking the target, because of the jacket constraining the target, hence there is generally less tissue damage. On the other hand, the harder jacket allows it to penetrate further into the target. One way to counteract the lack of expansion is to unbalance the bullet (make it heavier at the back) so that when it hits the target, it yaws in different directions as it penetrates the target. This is done by making the front of the bullet of lighter material, such as aluminium instead of lead.

A soft-point bullet expands when it strikes the target, since the front of the bullet is a softer material. Hence it generally causes more tissue damage than a full metal jacket bullet. However this expansion is limited by the outer jacket as well.

Another solution is to make the jacket cover the entire bullet, but make the tip of the bullet hollow, so that it expands when it hits the target. These bullets are called hollow point bullets or Jacketed Hollow Point (JHP). They were first manufactured in 1890 in a factory in Dum Dum, West Bengal, India and hence these bullets are also known as "dum dums." These bullets were quickly outlawed for military use by 1899, but they can be used by civilians and are used by hunters in many parts of the world.

GFDL licensed image from wikipedia.com

The above illustration shows three modern cartridges. Note how tapered these bullets are. The one on the left of the picture is a hollow point, as can be seen by the hollowed out shape at the tip. The bullet in the middle is a full metal jacket bullet. The one on the right is a soft-point bullet. Notice the tip of the soft-point is of a different color than the rest of the bullet, because it is a different metal.

As you may have noted above, the bullets of the three cartridges are extremely pointed This innovation in bullet design came from the French in 1898 for their Lebel 8 mm. rifle. They made the tips of their bullets more pointed, to improve the aerodynamic characteristics of the bullet and increase its range. Shortly after, the Germans copied the same idea in 1905 and called their bullets Spitzgeschoss or "pointed bullet". This gave rise to the term spitzer bullet, which is the generic English term for any bullet with a pointed tip. This concept was rapidly adopted through-out the world and now, virtually every country uses spitzer type bullets for rifles.

GFDL licensed image from wikipedia.com

In the above image we see two types of cartridges. The one on the left is a rifle cartridge that operates at higher velocities and hence it has a spitzer-type pointed bullet. The one on the right is a pistol cartridge. As you can see, it is a shorter cartridge and has a bullet with a rounded tip. This shape does not offer as much range or penetration as a spitzer-type bullet, but it is optimized for reliable feeding in an automatic pistol.

Monday, June 21, 2010

Bullets: Conical Expanding Bullets

In the 1800s, many people began to realize the advantages of rifling and started to make weapons that included rifled barrels. The problems associated with rifling were that if a bullet was too large, it would be difficult to insert it into a rifle and if it was too small, the gases would escape around the bullet and decrease its range.

The first breakthrough was by one Captain Norton who was stationed in India in the 1830s, who invented the first expanding bullet. He was followed in 1836 by Mr. William Greener, a well known Birmingham based gun-maker, who invented a compound bullet that could expand as it was fired. The British authorities paid little attention to their inventions and one of the reasons they rejected these bullets was because they were not spherical balls

In 1849, a Frenchman named Minie took the same idea and made a compound bullet called the Minie ball. We discussed all these three inventions earlier and the reader is invited to go back to that article and observe the pictures of the various bullets.

These were among the first conical shaped bullets that were used. Until then, the bullets were usually shaped as balls. A few years later, Mr. Joseph Whitworth, the pre-eminent mechanical engineer of his day was contracted to improve the rifle and he realized the value of elongating the bullet. The result was a new rifle that used polygonal bore and an elongated polygonal bullet to go with it:

We've also discussed the whitworth bullet in some detail in an earlier article and hence, we will not repeat that discussion here, other than to mention that these new bullets guaranteed better accuracy than the older spherical bullets. As a result of this, spherical bullets went out of fashion and the modern elongated bullet slowly started to gain in popularity.

Sunday, June 20, 2010

Bullets: Swaging

In our last post, we saw how smaller shotgun pellets are made. Pellets larger than 6 mm. cannot be made by this technique though and have to be made either by casting, or by using another method called swaging. We will study swaging in this post. Note that swaging is not used only for larger shotgun bullets, but also for making bullets in general. It can be used for making solid bullets, compound bullets, jacketed bullets, hollow point bullets, lead bullets, plastic bullets etc. Most major ammunition manufacturers use swaging techniques for making bullets today. It is ideally suited towards high-volume manufacturing, with very little variation between all the bullets made this process.

So what is this swaging process? It is generally a cold-formed forging process (i.e.) the work is usually done at room temperature, without heating the metal. It consists of a hard metal die which has a cavity of the desired shape of the bullet inside it. Lead or any other material is inserted into the die's cavity and then it is put under pressure by means of a metal punch which is forced into the die under pressure until it reaches a preset depth. The punch pushes the lead material (or other bullet material) into the shape of the cavity. The pressure to the punch may be applied by a manual press, a hydraulic press, repeated hammer blows, or by using a threaded punch that is screwed on. For most industrial-style manufacturing, a hydraulic press is used and the pressure applied is in the range of a few tons. The pressure applied depends on the hardness of the bullet material, its ductility, shape of the bullet etc. After the bullet material has been shaped, the punch is then removed from the die, the die is opened and the swaged item is removed. This process allows for uniform density and repeatability of process with very high accuracy.

If a bullet made of multiple materials is desired (e.g. a jacketed bullet, tungsten tipped bullet or a tracer bullet), then it can be done in multiple swaging steps, i.e. insert the first material into the die and apply a punch to make the first layer, then insert more materials and then apply the punch again for the second layer and so on.

This technique has several advantages over casting bullets. In casting, since the molten metal shrinks when it solidifies, the mold must be slightly larger than the desired size. Therefore it is harder to control the size of the final product. Since swaging happens at room temperature, the swaging die is the exact size of the bullet desired and therefore produces a more accurate-sized bullet. Swaging can be used to make compound bullets and jacketed bullets made of multiple materials, whereas casting can make bullets that are only composed of one material. Cast bullets may have defects such as air bubbles and cracks, whereas swaged bullets do not have these defects. Swaging can also be used to make non-metallic bullets, such as plastic bullets.

Saturday, June 19, 2010

Bullets: Shotgun Pellets

In our last post, we saw how lead balls were made by casting lead in a mold to form spherical bullets. The lead balls were used, one per shot, so the methods described in the previous post were used to manufacture them.

In the case of shotguns, different types of cartridges are used. In some cases, these contain a single large ball, in which case the previous methods of manufacture were used. However, certain types of shotgun cartridges use dozens of small spherical pellets instead of a single lead ball. In this case, manufacturing these small pellets using the casting techniques from the previous post is simply not practical. Instead, a different technique is used to manufacture these pellets. This technique is usually used to manufacture pellets up to 6 mm. in diameter or so, as it is not suitable for larger diameters.

We will first study the historical technique, which was invented in Bristol by one William Watts in 1782. The process starts by acquiring a location where lead may be dropped from a height of 40-60 meters. This could be a tower on the ground (called a shot tower), or an old mineshaft. In William Watts' case, he had a natural cave running under his house, so he built a three story tower and then dug a shaft in the ground till he hit the caves. There is a furnace at the top where lead can be melted. The molten lead is poured into a pan that has holes in the bottom of it, corresponding to the diameter of the pellets desired. The molten lead slowly percolates through these holes and forms globules which fall down to the bottom of the tower or mine shaft. During their fall, the molten lead globules become spherical shaped, much the same way as raindrops form spheres as they are falling so that surface tension is minimized. During their fall, the globules also harden in the air. At the bottom of the shot tower or mine shaft is a container filled with water. The fall through the air must be long enough for the pellets to harden sufficiently before they contact the water container, otherwise they will be flattened on impact. Typically, the pellets are dropped from a height of 40-60 meters for this to happen, though some shot towers are even taller. For instance, the Phoenix shot tower in Baltimore, MD, was the tallest building in the US at 234.25 feet (71 meters), when it was first built in 1828. The lead must not contain any zinc impurities and must have a small amount of arsenic in it, in order for the globules to form properly.

The more modern technique is the Bliemiester method invented by Louis A. Bliemiester of Los Angeles, CA and has been in use in the US since 1959. In this method, molten lead is dropped for a short distance of about 1 inch (approx. 25 mm.) into a container of very hot water. The pellets then roll down an underwater incline and then drop another 3 feet (approx. 1 meter). The hot water controls the rate that the lead pellets cool and harden and the surface tension ensures that the pellets are spherical. This method does not require a tall shot tower to be built and hence is the preferred method these days, while shot towers are now largely historical landmarks.

After the lead has cooled down, the shot pellets are gathered from the water container and classified into different shot sizes and any imperfectly shaped ones are removed and remelted. In the Victorian era, this was done manually by women who would gather the pellets in their aprons, dry them and judge whether each pellet was properly formed on not, by looking at them. The modern process is automated and is consequently faster. In the modern process, the shot pellets are taken out of the water container and put into a steam-jacketed tumbling barrel, where they are dried and polished. Next, they are taken to grading tables. These grading tables are located on an inclined slope and consist of a series of "steps" with gaps in between them. Each step is slightly lower than the previous one. The shot pellets are allowed to roll down the tables. Pellets that are sufficiently spherical shaped will jump across the gaps between the steps. Pellets that are improperly shaped or have multiple pellets fused into one, will not jump the gaps and will fall through into scrap boxes. The bad pellets are collected from the scrap boxes and remelted. The good pellets are taken through a series of vibrating mesh screens, each of which have a mesh of a particular size. The mesh screens sort out the pellets into standardized sizes, by keeping pellets above a certain size on top of the mesh, while allowing smaller sized pellets to drop through them. These sorted pellets are then packed into bags and shipped out to a cartridge manufacturer.

If the pellets made with this technique are made of pure lead, then they are known as drop shot. If a small amount of antimony is added to the lead, then these pellets are known as chilled shot. Pure lead pellets are somewhat softer and thus they get deformed more when fired with more powerful cartridges. Addition of antimony to the lead makes it an alloy that is a bit harder and can withstand higher pressures.

As mentioned before, this technique can only be used for smaller diameters (less than 6 mm. or so) and larger shot must be manufactured using casting or swaging techniques. We have already studied casting in the previous post and we will study swaging in the next post.

The sorted pellets are used by cartridge manufacturers or home reloaders to manufacture cartridges.

Friday, June 18, 2010

Bullets: Early Bullets

In the early days of firearms, bullets were mostly made of cast lead balls. When we look at early firearms such as the petronel, culverin and matchlock weapons like the arquebus, these were essentially hand made weapons and the user was often the same person who helped build it. None of these weapons were built to any particular standard and hence, each weapon was supplied with its own bullet mold, so that the user could cast their own bullets as needed. Even when weapons like the caliver (which was built with a standard bore size and gave us the English word "caliber") were introduced, users were often supplied a set of bullet molds with them.

What we have here is an antique musket's bullet mold. This type of mold is called a scissors mold and is made of cast iron. The specimen is a bit pitted due to wear and tear, but still works very well when it comes to casting bullets. It looks similar to a pair of pliers, except that the jaws enclose a hollow spherical section in between them. The picture below shows the view of the other side of this mold.

As can be seen from the above picture, the two scissor arms can be manipulated to open or close the mold as needed. The picture below shows how the mold looks from the inside, when the jaws are opened.

To cast a ball, the user initially melts a quantity of lead in a container. Then the user closes the mold and pours in some lead through the hole on top. The lead quickly cools and solidifies inside the mold. Next, the user opens the jaws by manipulating the scissor arms and extracts the bullet. This bullet is mostly spherical except for a tiny bit of projecting metal, called the sprue which is formed by lead hardening in the hole through which the lead was poured through. There is usually a thin parting line formed around the ball as well, along the line where the mold opens. The lead bullet is taken out and then the sprue and parting lines are filed off, to leave behind a spherical bullet.

Of course, using a mold like this is slower work, since the user can only produce one bullet at a time. It must be said that lead does solidify fairly quickly, but this is a slow process even then. A faster way to handle this is a multi-bullet mold, something like the example shown below:

In the diagram above, we see a design plan of a hinge-type bullet mold. In this one, the jaws are closed and molten lead is poured down the groove in the middle of the jaws. After the lead cools, the jaws are opened to reveal four bullets which can be cut free from the sprues and then filed down to spheres. The left over lead from the casting can be remelted for the next batch.

The picture above shows a multi-bullet mold used for the famous Brown Bess musket, which served British forces for over one hundred years. This particular mold is made of soapstone and comes in two halves. Note the two wooden pins sticking out of the center of one half of the mold and the two corresponding holes in the middle of the second half. These pins are used to make sure that the two halves of the mold are properly centered. The two halves of the mold are brought together and then molten lead is poured through the holes along the edges. After the lead is allowed to cool, the two halves of the mold are separated and eight musket balls are taken out. As before, the balls are mostly spherical, but they have a little extra projection where the lead has cooled at the holes through which the lead is poured in. There is usually also a little thin parting line around the circumference of the ball corresponding to the two halves of the mold. These projections must be filed out and then the balls are ready to use.

It must be remembered that there are a few issues with metal casting. For one, the molten metal must be poured into the mold slowly, so that the air inside the mold is allowed to escape, otherwise the cast bullet may have air bubbles trapped inside it. Also, molten metal occupies a bit more volume than solid metal, so the casting shrinks a bit when it solidifies. Hence, the final casting is a bit smaller than the mold itself.

As these balls were mostly used with muzzle-loaders, the size of the ball was generally a bit smaller than the diameter of the musket bore, so that these were easy to load into the firearm. For example, a Brown Bess musket's bore was 0.75 inches, so the balls produced by this mold would be something like 0.69-0.70 inches in diameter. The user would first pour some gunpowder down the barrel, then take a ball and wrap it around a greased patch to provide lubrication and a tighter fit and then ram the resulting package into the barrel.

Spherical lead balls were in use for a very long time between the 1200s and 1800s or so and it was not until the 1820s that people started to slowly go for other types of bullets. These bullets are still used today by certain hunters who wish to hunt like their ancestors did.

Thursday, June 17, 2010

Bullets: Basics

After reading up about different types of propellants, we will now study the history of bullets. It may come as a surprise to some people to realize that the history of bullets predates the history of firearms. Bullets have been found in some of the ancient ruins around the planet. These bullets were not fired from firearms, but were fired from slings and handheld catapults. Some of these bullets were made of stone, others were made of metal.

The word "bullet" derives from the French word, boullet, which means "little ball". A lot of the early bullets were spherical balls and it wasn't until the 1820s or so when the bullets started to change shape.

When it comes to bullets for firearms, one thing is common to all of them, whether they were made in the 1200s or in the 2000s. A majority of them have a large percentage of lead. There are a few good reasons why this is the case.

In order to be a good bullet making material, the following characteristics are desirable:
  1. Density: The bullet must be made of dense material so it can pack as much mass as possible in a given volume.
  2. Low cost
  3. Easy to shape
  4. Availability of materials.
Lead seems to fit all these features admirably for small arms ammunition. By looking at the periodic table of elements, the reader will be hard pressed to find another element that is plentiful in nature, but has a higher density than lead. The elements above lead in the periodic table are either rare, volatile, gaseous, radioactive, expensive to extract from the ore or a combination of these properties. For instance, tungsten and uranium are denser than lead, but they are expensive to produce and harder to machine than lead. Hence people use depleted uranium and tungsten only for making special armor-piercing ammunition, but not regular small-arms ammunition. By contrast, lead is very easily available in nature, has high density and is a soft material with a low melting point (which makes it easy to shape). As an extra bonus, it is also a toxic substance.

One of the problems of lead is that it is a soft substance. With firearms before the 1800s or so, this wasn't a problem because the propellants used weren't as powerful and hence the pure lead bullet worked just fine. As propellants got more powerful, the soft lead bullets would get deformed too much before they left the barrel and they would also melt a bit due to the heat. These deformations affected the flight of the bullet. The solution was to encase the lead in a jacket of a harder material such as steel, cupronickel, copper etc.

In the next few posts, we will study the evolution of bullet development.

Propellants: Smokeless Powders

In the last couple of posts, we studied the manufacturing techniques of black powder. In this post, we will study the next development of propellants, namely smokeless powders. First, let's get a couple of common misconceptions out of the way:
  1. There is no single smokeless powder. Instead, the term applies to a number of different powders, all made of different ingredients.
  2. Smokeless powders are not truly smokeless. It is true that during combustion, most smokeless powders burn up most of their mass into gaseous products, unlike black powder, which leaves behind 55% of its weight as solid residue. However, there is still some smoke produced.
Smokeless powders provide much more propellant force than the same amount of black powder, which made it possible for weapon ranges to increase. Since smokeless powders don't leave behind as much residue as black powder does, the weapons require less cleaning after use. The development of semi and full-auto weapons was also made possible because of the fact that there is very little residue and thus cannot easily jam the many moving parts of an automatic weapon.

While we noted in our post about propellant basics, that materials classified as "low explosives" are suited for propellants, smokeless powders generally contain a good percentage of high explosive materials such as nitroglycerine (go read the post on propellant basics to understand the difference between low explosives and high explosives and why low explosives are used with firearms). The way it works is that even though the propellant has a high explosive substance, a stabilizing chemical is also added to slow down the burn rate of the high-explosive so that it behaves more like a low-explosive.

The first smokeless powders were made in 1846, when both nitrocellulose (gun cotton) and nitroglycerine were first developed in Europe. The invention of gun cotton was actually the result of a happy accident. A Swiss scientist named Christian Schonbein was forbidden by his wife from conducting chemistry experiments at home, but he didn't always obey her. One day in 1845 when she was away, he accidentally spilled a mixture of strong nitric and sulfuric acids in the kitchen. He quickly wiped the mess up with his wife's cotton apron and then hung it over the stove to dry. To his surprise, the apron ignited and disappeared almost instantly, leaving behind almost no ashes. What Schonbein had done was accidentally manufacture nitrocellulose. Soon, with the help of another professor, he came up with the recipe of one part of fine cotton fibers, combined with fifteen parts of an equal blend of sulfuric and nitric acids. The cotton is dipped in the acid mixture for two minutes and then washed in cold water to remove any acids. Then the cotton is dried at moderate climate temperatures to form nitrocellulose. This material provides less heat and smoke and upto six times the explosive force of the same volume of black powder. However, guncotton was notoriously unstable and therefore, the British, French and Prussian governments stopped using it soon after. However, the French continued to perform experiments to improve its stability.

In 1884, a French chemist named Paul Viellie succeeded in improving guncotton's stability issues. He discovered that by treating guncotton with a mixture of alcohol and ether, it could be gelatinized. The material could then be rolled into sheets, cut into small squares or flakes and then stabilized with a 2% solution of diphenylamine. This formulation was codenamed Poudre B by the French government and it was a closely guarded secret. This formula produces a substance that is much more stable than guncotton and it will not detonate unless it is compressed. Unlike black powder, Poudre B also burns when wet and produces about three times the force for the same volume. This was the first "single-base" powder. The French developed the 8 mm. Lebel cartridge (the first smokeless military cartridge) and a new rifle, the Lebel Model 1886 to use this new technology.

In 1888, Alfred Nobel (the same person who started the Nobel prizes) discovered that he could gelatinize nitrocellulose by using nitroglycerine. The chemical formula was 45% nitroglycerine, 45% guncotton (nitrocellulose) and 10% camphor. He started to market his invention as "Ballistite" and it was the first "double-base" powder. The presence of nitroglycerine gave ballistite an even greater range than Poudre B. Nobel Industries set up a plant in Scotland to manufacture ballistite.

In the very next year, the British government appointed an "Explosives Committee" to monitor and study developments in other countries. They obtained samples of Poudre B and Ballistite, but decided that neither was suitable for adoption in UK. Two of the committee members, Frederick Abel and James Dewar, discovered that by combining 58% nitroglycerine, 37% guncotton (nitrocellulose) and 5% vaseline and dissolving the mixture in an acetone solvent, they could produce a paste which could be squeezed through a die to form a long thin string or cord of 1 to 5 mm. diameter depending on the application. From the cord, small pieces and shavings could be cut mechanically using a knife or a file, or it could be ground up using a device similar to a coffee grinder. In most cases, it was cut into small strings and packed into a cartridge case like spaghetti. This material was naturally given the name "cordite". It is also a double-based explosive like ballistite and later, a triple-base cordite was also invented. Abel and Dewar were the target of a lawsuit by Alfred Nobel, who felt that they had merely modified Ballistite slightly. The case took several years to be resolved and eventually reached the House of Lords, where the court ruled in favor of Abel and Dewar.

Disassembled cartridge. Note the light brown strings of cordite which were packed inside it.

An interesting feature of cordite (and some other smokeless powders as well) is that if the strings are burnt outside the cartridge, then they burn rather slowly with a yellow flame and no explosion. Cordite only explodes if it is lit in a confined space (such as a cartridge packed with cordite). It is also very resistant to shock. For example, it is possible to shoot cordite with a rifle bullet and still not explode it.

The first version of cordite was labelled Cordite Mk-1. The original version was the cause of early gun barrel erosion and so a new version was invented. This version had 65% guncotton, 30% nitroglycerine and 5% vaseline and was dissolved in acetone and was dubbed Cordite MD (MD for Modified). This version did not damage the barrels as much, but exploded with lesser force than Cordite Mk-1. Hence the cartridges were made to contain 15% more material to maintain the same force as Cordite Mk-1.

During WW-I, due to a shortage of acetone, Chaim Weizmann (later, the first president of Israel) invented another formula for use by the Royal Navy. This formula was called Cordite RDB (for Research Department Formula B). It was made by combining 52% guncotton, 42% nitroglycerine and 6% vaseline. Cordite SC (SC = Solventless Cordite) was invented before WW-II and used for larger guns (such as anti-aircraft). Another development in WW-II was Cordite N. This was made by combining cordite with nitroguanine, which is another explosive. Cordite N was the first triple-base explosive.

Despite all the improvements, cordite started to lose popularity around the middle of WW-II when newer propellants were invented. By the end of the 20th century, the last cordite manufacturing plant closed down.

One series of powders developed during WW-I to replace cordite was called IMR (Improved Military Rifle), which was developed by Dupont to replace the older MR (Military Rifle) series of powders. There were a number of IMR powders developed between the two World Wars. They are made of nitrocellulose, but contain dinitrotoluene (DNT) to slow down the burn rate of nitrocellulose to a low explosive. Graphite is also added to minimize static electricity and a small amount (0.6%) of diphenylamine is used as a stabilizer. A small amount (1%) of potassium sulfate is added to decrease the amount of muzzle flash. The powder is extruded out in the form of sticks. Different IMR powders were used to manufacture such famous cartridges as the .30-06 used by Enfield and the Mauser 7.92x57 mm. IMR powders are still used to this present day and are sometimes known as "stick powder" because the process of extrusion creates sticks of the propellant.

In 1933, another invention was the ball-powder propellant. This is made by dissolving guncotton in ethyl acetate and then forming the round grains under water. This process is similar to how round oil droplets are formed when mixing oil in water and shaking the contents of the bottle. Nitroglycerine is added to the grains to increase the explosive force and dinitrotoluene or a similar substance is added to slow down the burn rate. Like IMR powders, there are a number of ball powders as well using slightly different proportions and different substances to slow down the burn rate. Ball powders started to gain popularity in the 1950s. For instance, the ball powder WC 844 is currently used in the NATO 5.56x45 mm. cartridges.

The advantages of ball powder over other types of smokeless powder are many. For one, it takes a lot less time to manufacture than other types. Most other smokeless powders take a few months to manufacture. Dupont did manage to get one IMR powder type to be manufactured in 2 weeks. In contrast, one production lot of ball powder could be made in under two days. Ball powder can also be stored longer than other types. Excess acids during the manufacture of smokeless powder cause the powder to deteriorate more quickly. The ball powder manufacturing process is more efficient in eliminating most of the excess acid and it doesn't produce much acid as it ages either. The manufacturing process is also safer as it happens under water and also requires much less specialized equipment to set up a manufacturing line.

Tuesday, June 15, 2010

Propellants: Black Powder - II

In our last post, we studied the basic components of black powder and how they were obtained throughout history. In this post, we will study the history of its manufacture.

The three ingredients, namely potassium nitrate (or sometimes sodium nitrate), charcoal and sulfur are ground up into powder and mixed together. In the earliest processes, the dry ingredients were all put into a grinding apparatus (usually a mortar and pestle) and ground together into a powder mixture called a "serpentine". The exact proportions of the three components in the middle ages were varied from country to country. It is known that England was using a 6:2:1 ratio by weight in the 1350s, while the Germans were using a ratio of 4:1:1 during the same period. The French also had black powder, but it is not known what ratio they were using. In fact, the various proportions of the ingredients and the technique of making high quality charcoal were both closely guarded state secrets throughout most European kingdoms. There were a few issues with black powder manufacturing during this period. One was that the mixing process was highly dangerous since the materials are highly inflammable. The second was that there wasn't much consistency in the final product, so one batch of powder would have better shooting properties than another batch. The third issue was that since the powders of the three ingredients were not the same sized particles, if the powder was transported by cart to a battlefield, chances were very good that the vibrations would make the smaller ingredient particles settle in the bottom of the box. This meant that the serpentine powder would need to be mixed again thoroughly, just before use.

One of the major inventions to improve this situation came out of Europe in the late 1400s or so -- a process called "corning". The powder manufacturers of medieval Europe had realized early on that the way to reduce a large portion of the risks of the manufacturing process was to wet the ingredients with water or wine first and grind them separately and then mix the wet ingredients together. Then the resulting black-powder could be dried in the sun before use. They also realized that the ingredients could be mixed wet and pressed into cakes of a given uniform density (1.7 gm/cc is ideal). The cakes could then be dried in the sun where they become hard and brittle.

Black powder pressed into cakes of uniform density

The cakes could then be broken into grains or corns and these grains could then be sorted into standardized sizes by passing them through various sieves. This whole process was a major improvement, because it fixes all the problems enumerated earlier. In fact, all black powder manufactured to this day is still corned.

Different containers of corned black powder sorted by grain size

The Europeans experimented with manufacturing various grain sizes and determined that larger grains are more suitable for larger guns and cannons and smaller grains, which are quick burning, are more suitable for pistols. Hence, they were the first to produce different types of gunpowder, each of uniform grain sizes. Because of this uniformity and consistency, European gunpowder was generally regarded as higher quality than gunpowder manufactured in America or Asia. However, not all European countries were producing quality black powder. W.W. Greener's book, The Gun and its Development from the mid 1850s, mentions that powder in England is of various grades and makers like Curtis & Harvey and Pigou, Wilks & Lawrence make some quality powders. He says that a grain size classified as "African" is very good for export purposes, but cautions to buy a powder marked "Brazil" designed for export to South America saying that it looks very attractive because it is highly glazed, but is actually a very poor quality powder. Apparently, the South Americans valued its shiny looks more than its shooting properties and the author mentions that the only reason to buy this is for trading purposes. He says that Spanish powder quality varies upon locality and that the Swedes and Norwegians make very good quality powder, but unfortunately in limited quantities for their own markets only. He also says that German powders also vary depending on locality, but some are very high quality, sometimes even exceeding the finest English powders of the time. He classifies the powders made by the French (and all the French possessions at the time) to be the worst quality and full of dust, due to the fact that the manufacture of black powder was a monopoly held by the French government at that time and they didn't allow imports of black powder from other countries either.

By the 1750s, the ratio of 15:3:2 by weight (i.e. 75% potassium nitrate, 15% charcoal and 10% sulfur) was becoming common in most of Europe and by 1800, it was the ratio used around the world and is still the standard today.

The process of manufacturing corned black powder is still the same, except that since the 1800s, the process of grinding and mixing the materials has been largely automated. In the early 1800s, the common type of mill used for grinding was the edge runner mill. This is an ancient type of mill that was invented in China in the 5th century AD and spread to Europe about 800 years later. It was commonly used for hulling rice and crushing ore. It consists of one or more heavy disks set on their edges and a circular lower milling trough or tray. The disks roll around the trough in a circular path and crush everything in their way.

Public domain image courtesy wikipedia.com

These mills were usually driven by water power and therefore the powder factories were located close to rivers. Edge runner mills are still used in food processing today and are seen in some chocolate factories.

Most modern processes use a ball mill to do the job. It consists of a hollow cylinder into which the raw materials are put in. There are also a number of balls made of lead, brass or bronze put into the cylinder. These materials are chosen because they are non-sparking in nature. The materials are put in the cylinder and water or alcohol is added to keep it wet. The cylinder is then closed and rotated about its axis for about 3 hours.

The balls rub among themselves and grind up the raw materials between them into a fine powder. After some time, the cylinder is opened and the ground up material is extracted. In some cases, the three ingredients are ground up separately and then combined later. In other cases, the three ingredients are put into the mill simultaneously and ground up together. The three powdered ingredients are mixed together when wet and then pressed into cakes, which are dried and then broken up into grains which are sorted by sieves into various standardized sizes.

Black powder was the only propellant used between the 1200s to the late 1800s or so. One of the problems with black powder is that it leaves behind a lot of residue, which means that guns need to be cleaned every few shots or so. The invention of smokeless powders in the late 1800s reduced the need for black powder, since smokeless powders burn cleaner and with more power than black powder. These days, the only users of black powder are those that wish to hunt with weapons similar to what their ancestors used.