Friday, December 27, 2013

Is it a shotgun or a rifle? The Paradox gun

In the 19th century, the British Empire spanned a large portion of the globe. This was a time when rich English sportsmen would undertake expeditions to remote parts of the world to hunt exotic birds and animals. To hunt small targets that could be approached at closer ranges (e.g. birds, rabbits etc.), the best weapon that hunters could use were shotguns and to hunt larger furry animals that needed to be shot at longer ranges (e.g. deer, buffalo, tigers etc.), hunters would use rifles.

However, this meant that sportsmen would need to carry two different kinds of firearms for their expeditions: shotguns and rifles. Bear in mind that rapid reloading technologies were not yet fully developed at that time and the standard method of hunting in these expeditions was for the hunter to carry one loaded firearm and have a few assistants (called "gun bearers") standing next to him, each carrying another loaded firearm or two. After the hunter had fired his weapon, one assistant would exchange his loaded firearm with the hunter, so that the hunter could continue firing at targets, while the assistant reloaded the other firearm. Also, because there was a chance of parts breaking in the field, a hunter would typically pack several rifles and shotguns for an expedition, so that he would not have to return early, if one firearm broke.

Sportsmen of that era, expected to hunt both birds and animals on a long expedition and hence, they would pack both shotguns and rifles for their journeys. This made their baggage heavier, since these are two different firearm types. This was the situation until 1885, when a British colonel named George Vincent Fosbery, invented a firearm that could be used as both a shotgun and a rifle. His invention consisted of a large shotgun with a mostly smooth barrel, but the last few inches of the barrel near the muzzle were rifled with a special "ratchet" style. The famous British firearm manufacturer, Holland & Holland, immediately bought the patent rights for this firearm and began to market it as the Paradox gun in 1886.

Patent document from 1885 showing the design of the Paradox gun's special barrel.
Click on image to enlarge. Public domain image.

Muzzle of a 12 bore Paradox gun showing the special rifling.
Click on image to enlarge. Image licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license by user "Lord Mountbatten" at wikipedia.

19th century advertisement for the Paradox Gun. 
Click on image to enlarge. Public domain image.

The word "paradox" means a statement that apparently contradicts itself. The reason that Holland & Holland chose to market this firearm with this name was because the defining nature of a shotgun of that era was its smooth barrel, but this was a shotgun with rifling in the barrel, hence it was a paradox!

The hunter could now carry one gun and two different types of cartridges and load the appropriate cartridge type, depending upon the target. Holland & Holland built about 1500 Paradox guns of various sizes between 1886 and 1930. They were built for a variety of bores: 8, 10, 12, 16 and 20 gauge.

While Holland & Holland owned the trademark "Paradox gun", they were not the only manufacturer of this type of dual-use firearm. Other British manufacturers made them for sale under their own names or for other companies to sell under their brand names (e.g.) Westley Richards and G & S Holloway. Westley Richards started manufacturing these guns in 1905 and sold them under the trademarks "Explora" (for larger bore 12-gauge gun models) and "Fauneta" (for smaller bore 20 and 28 gauge gun models). Some of G & S Holloway's products were resold in India by P. Orr & Sons, a high end jeweler and watch dealer in Madras (now Chennai), India, so their products are marked with both G&S Holloway and P. Orr markings. Some of these firearms occasionally show up in firearm auctions. P. Orr & Sons are still in business, although they have stopped selling firearms since around 1970 and only sell clocks and watches now.

Vintage advertisement by Westley Richards for their Explora model gun. Click on image to enlarge

In 2006, Holland & Holland announced that they would start manufacturing Paradox guns again, after a break of over 70 years and they are currently selling new models.

Friday, December 13, 2013

The M1895 Nagant Revolver

In our last post, we talked about the concept of "cylinder gap". Briefly, revolvers have a gap between the cylinder and the rear of the barrel, in order to allow the cylinder to rotate freely. However, when a revolver is fired, some of the hot gases will escape through this gap, possibly flushing some metal particles as well, which is why it is dangerous to have body parts close to the front of the cylinder. We discussed all of this in our last post (please read it, if you haven't already done so). We also pointed out that due to some of the gases leaking out of the cylinder gap, this decreases the velocity of the bullet coming out of the revolver. In today's post, we will look at a revolver that attempted to solve this problem. We are talking about the Nagant M1895 revolver, which will be the subject of today's post.

The Nagant M1895 was a revolver designed in 1895 by Leon Nagant, for the Russian empire. The Nagant Brothers company was Belgian, but they were well known to the Russian military, because they were involved in an earlier competition to design a new rifle for the Russian military previously (the result of the earlier competition was the Mosin-Nagant M1891 rifle, although Nagant's contributions to the final design was very minimal).

The Nagant revolver design attempted to minimize the velocity loss, by making the revolver gas-tight as possible. We will discuss how this was achieved here.

Mosin-Nagant M1895 Pistol. Click on image to enlarge.
Image licensed under Creative Commons Attribution-Share Alike 3.0 Luxembourg license by user Mascemon @ wikipedia

At first glance, the revolver appears to have a pretty large cylinder gap, as can be seen by the image above. However, the revolver is built with a special mechanism, so that when the hammer is cocked, the cylinder not only rotates to the next chamber (just as any other revolver), but it is also pushed forwards toward the barrel, thereby closing the cylinder gap and creating a seal with the forcing cone at the back of the barrel.

Now, the cylinder is just one part of the gas-tight seal. Let's take a look at the unusual cartridge for this revolver. Here's a closer look at it:

From left to right, Nagant 7.62 mm., .32 S&W Long and .22 Long Rifle (.22 LR) cartridges.
Picture courtesy of Commander Zulu at Wikipedia.

The cartridge on the left is the one for the Nagant revolver. Compared to the other two cartridges, a few differences are clearly visible. Unlike the other cartridges, the Nagant cartridge fully encloses the bullet inside the cartridge case. Note that the neck case of the cartridge is crimped to a smaller diameter and the bullet does not protrude out of the end. This is part of the design. When the cylinder is moved forward into the forcing cone, the cartridge's unusual neck is forced between any gap left between the cylinder and the forcing cone. When fired, the neck expands into the forcing cone and fills any remaining gaps, making it even more gas tight. As a result of this, the Nagant M1895 does not leak much gas through the cylinder gap when it is fired, and the bullet comes out about 50-150 feet/sec (15-45 meters/sec) faster when it is fired.

As we saw in an earlier post, temperature has an effect on ammunition performance. By making the gas seal tight as possible, this revolver could perform better than other models, even in the middle of very cold Russian winters and with the types of propellants that were available in 1895. A couple of other side-effects are a result of this gas seal design as well. For one, it reduces the chances of injury to body parts in front of the cylinder, because the hot gases and particles don't come out of the side as much. Also because of the gas seal, the noise generated comes out of the barrel, which means that unlike other revolver models, this one can be fitted with a suppressor to reduce the noise.

The video above shows the unusual mechanism and cartridges in very good detail.

This revolver was used a lot by the Russian Empire and then, the Soviet Union, and is used even today by present-day Russian police, despite being out of production for about 60 years. It is regarded very highly in Russia for its toughness.

However, there are a few disadvantages of this revolver as well. The first is that it is much slower to load this revolver than other models. Because of its design, the cylinder cannot flip out of the side to load the cartridges simultaneously. Instead, the user must load and unload each chamber one at a time, via a loading gate on the side. Also, this ammunition does not have great stopping power compared to more modern cartridges. At one time, it was difficult for American users to purchase ammunition for this revolver, even though the revolver is pretty cheap to purchase (typically costs about $100). The trigger is also pretty heavy to use and accuracy suffers as a result.

Before we end this discussion, here's another video done by the same user above (hickok45), demonstrating the effectiveness of the unique gas seal of this weapon.


Tuesday, December 10, 2013

What is a "Cylinder Gap"?

In today's post, we will look into the topic of revolvers and firearms safety and also study the concept of cylinder gaps.

If the reader looks at a revolver, chances are that the reader may observed that, at the area where one of cylinder's chambers aligns with the barrel, there is a small gap between the front of the chamber and the barrel, about the thickness of a business card. This space is called the cylinder gap.

This gap exists in all revolvers, because there needs to be a bit of space between the cylinder and the barrel, in order to allow the cylinder to rotate. In some revolver designs (e.g. the Belgian Nagant 1895 model), this gap is sealed when the weapon is cocked (we will look at this design in a future discussion), but in most revolver designs, this gap is left open at all times.

When a revolver is fired, high pressure gases are generated in the chamber and expand into the barrel, pushing the bullet out. While most of these gases expand into the barrel, a small amount of hot gas comes out of the sides of the cylinder, due to the cylinder gap. If the chamber does not precisely align with the barrel, some metal particles may come out of the side as well. These hot gases and particles come out with a surprising amount of energy, even on a small revolver, and may cause some serious injury. Therefore, it is unwise to place a hand ahead of the cylinder, or even stand close to the side of the person firing the revolver.

Correct ways to hold a revolver

In the above images, we see the correct ways to hold a revolver. Notice that in both cases, the person ensures that the hands are placed well behind the cylinder gap. Now we will look at the incorrect way to hold a revolver.

Incorrect way to hold a revolver. Never do this!

In the above image, we see an incorrect way to hold the revolver. Notice that the user has some fingers placed in front of the cylinder. This is a very bad idea and could result in serious injury, if the revolver is fired. People who are new to revolvers may accidentally do this, because they find it easier to support a heavy revolver, or because they see people doing it with pistols, and they cause injury to themselves.

The above video demonstrates pretty well, how much gas can come out of the sides of the cylinder and why it is a bad idea to put any body parts close to the cylinder gap. In fact, people standing close to the sides of the revolver may feel the hot gases as well, which is why it is best to stand behind the shooter, or some distance away to the side.

The reader may wonder, why is it that gases don't come out of the back of the cylinder? Well, that is because when the revolver is fired, the heat of the explosion causes the sides and back of the cartridge to expand slightly and the rim seals off the back of the cylinder and prevents most of the gas from leaking out of the back.

Due to the leakage of gases through the cylinder gap, the velocity of the bullet coming out of the revolver is slightly reduced. There are designs that attempt to close this gap when firing, so that the entire energy of the expanding gases acts upon the bullet. We will study these designs in a future post.

Friday, November 29, 2013

The M16 Family III - The Clones

A couple of posts ago, we looked at various members of the M16 family. All of the models we have looked at so far, have been developed for the needs of the American military. In today's post, we will look at some more members of the M16 family that were developed by other countries.

In 1984, Canada decided to equip their military with a new rifle and wanted to go with the NATO standard cartridge 5.56x45 mm. In order to save development time and money, they decided to purchase the license to manufacture M16s of their own. A little while earlier, the US Marines were working towards improving the M16A1 model to the M16A2. A Canadian military liaison officer was also present while the Marines were working on improvements and he communicated some of these design changes back to Canada. As a result of this, the Canadian C7 rifle was developed with some features of the M16A1 and some of the M16A2. A Canadian company, Diemaco, was put in charge of manufacturing the new rifle.

C7 (top) and C7A1 (bottom) rifles

The C7 rifle has the stronger and longer stock, barrel with 1 turn in 7 inches twist rate, pistol grip and handguards of the M16A2, but retains the older rear sights of the M16A1, as well as the same firing modes of the M16A1 (single shot and fully automatic). One more major difference, which is not obvious, is that the C7 barrel is manufactured by the hammer-forging process.

The C7A1 incorporated some improvements to the C7, the main one being the replacement of the carrying handle, with a rail that allows the user to attach other devices here, such as iron sights or optics. This is similar to the M16A4 model, however the C7A1 preceded the adoption of the Picatinny rail by the US military, therefore the rail on the C7A1 is of slightly different dimensions than the now standard picatinny rails.

The C7 and C7A1 models are now being replaced by the C7A2 model in the Canadian military. The C7A2 has picatinny rails, in order to be standards compatible with all the accessories that are made to fit on a picatinny rail. It also has rails in front to attach laser pointers or lights. Unlike the previous models, it has a telescoping stock. One more major difference is that the C7A2 rifle furniture is green in color, instead of black. Other changes include ambidextrous magazine release and ambidextrous safety selector levers.

The C7A2 model rifle

The C7 family also comes with corresponding carbine variants, the C8, C8A1 and C8A2. The C7 and C8 families are used by the military forces of Canada, Netherlands, Denmark, United Kingdom (Special Forces mostly), Norway (Special Forces), Canadian Police etc. In 2005, Diemaco (the company that made the rifles in Canada) was bought out by Colt and is now known as Colt Canada.

Another manufacturer of M16 clones is Singapore's ST Kinetics, which produces the M16S1 for Singapore's military. The M16S1 is simply a M16A1 made under a license by ST Kinetics.

Another clone of the M16 family is the Chinese made Norinco CQ. Unlike the C7 family, the Norinco CQ is an unlicensed clone of the M16. While it uses the same 5.56x45 mm. cartridges of the M16, the Norinco CQ was never adopted by the Chinese military. However, they make two models for export, one capable of selecting between single shot and fully automatic fire for military sales and a semi-automatic only version for civilian markets.

Public domain image of a Norinco CQ rifle. Click on the image to enlarge.

It is pretty easy to tell a Norinco CQ apart from other members of the M16 family. First, notice the shape of the stock is completely different from the M16A1, M16A2, C7, C7A1 etc. Second, the handguards in front are also differently shaped than the other members of the M16 family. Thirdly, the pistol grip is curved on the Norinco CQ. Fourthly, the front sight on a Norinco CQ is of the hooded sight type, instead of a sight post.

The barrel of a Norinco CQ has a 1 turn in 12 inches twist rate. Because of this twist rate, it will fire the M193 cartridge designed for the M16A1 properly, but cannot accurately fire the NATO standard SS109 or the newer US M855 cartridge beyond about 100 meters or so (because these require a twist rate of 1:7 for stability in the air).

While the military version of the Norinco CQ was never used by the Chinese military, it is used by military forces of some other countries, such as Cambodia, Syria, Libya, Iran (which makes their own copies of the Norinco CQ), Sudan etc.

Sunday, November 24, 2013

Performance considerations for the M16 Family

In our last post about the M16 family, there was an interesting comment by a long time reader of this blog, Mr. Wojciech Imbierowicz. He questioned the ballistic performance of bullets on the M4 rifle, as compared to the M16A2. That will be the subject of today's post.

The first thing we will discuss is the relationship of bullet velocity to barrel length. When a cartridge is fired, the pressure of the expanding gases in the barrel is responsible for accelerating the bullet. As soon as the bullet leaves the front end of the barrel, the gases stop acting upon it. Therefore, the maximum velocity of the bullet is at the tip of the barrel and it starts to decelerate after it leaves the barrel. Obviously, if we have a shorter barrel, then the gases will not have a chance to accelerate the bullet much, before it exits the barrel. If we have a longer barrel, then the expanding gases will act on the bullet for a longer time and be able to accelerate it to higher velocities. Of course, there is a certain point in the barrel length, beyond which, increasing the length produces diminishing gains in the velocity of the bullet. Also, if a barrel is too short, the propellant may not entirely burn inside the barrel, which also reduces the force that is acting upon the bullet. On a longer barrel, the entire propellant may burn inside the barrel.

Depending on the type of cartridge, the optimum barrel length for maximum velocity may vary. The following table shows us some numbers for two common cartridges used by the M16 family, the M193 (the original cartridge that was used with the M16A1) where the bullet weighs 55 grains, and the SS109 (the NATO standard cartridge), where the bullet weighs 62 grains.

Barrel Length
(in inches)
Velocity (M193)
(Feet per second)
Velocity (SS109)
(Feet per second)

As we can see from the above chart, barrels that are between 16 and 20 inches in length seems to be the sweet spot, after which, the increase in barrel length doesn't increase the velocity of the bullet by that much.

Now on to one more feature of the bullets used by the M16 family. The 5.56x45 mm. bullet is pretty small, but it has an interesting property that if it is travelling above a certain velocity when it hits a target, it tends to fragment and produce a wound much larger than the size of the bullet. Below this velocity, the bullet does not fragment reliably and produces a much smaller wound. For the M193 cartridge, this threshold is approximately 2700 feet/sec and for the SS109, it is approximately 2500 feet/sec. Of course, the material of the bullet and its construction also have a lot to do with how much velocity they need to fragment reliably. For the purposes of this discussion, we will only consider the two above-mentioned cartridges.

Now, from the table above, we see that if the barrel is 10 inches long, the velocity of the M193 bullet (2739 feet/sec) is just barely above its the fragmentation velocity (2700 feet/sec). The same is true for the SS109 bullet as well. Therefore, for both these cartridges, the bullet's velocity will fall below the fragmentation velocity pretty quickly beyond about 20 meters or so. For the record, the 10 inch barrel is used by some civilian and police forces AR-15 models.

With the 14.5 inch barrels (such as those used by the military's M4 carbine), we see that the velocities are somewhat higher (3064 feet/sec for M193 and 2907 feet/sec for SS109). This means that the bullets will travel about 100 meters before their velocities fall below the fragmentation threshold velocity.

Now, with the 20 inch barrels (such as those commonly used by AR-15s, M16A2 etc.), the velocities are a bit higher and therefore, the bullets can travel about 150-200 meters before they will stop fragmenting reliably. Therefore, between 100 to 200 meter distances, they generally have better wounding performance than bullets fired out of a M4 carbine, which only has a 14.5 inch long barrel.

To improve the performance, the US military has come up with some newer bullet designs that have lower fragmentation velocity thresholds. The newer M855A1 and the Mk 318 cartridges were specifically designed to handle some of the shortcomings of the previous cartridges.

Thursday, October 31, 2013

The M16 Family - II

In our last post, we looked at some members of the M16 family. We also mentioned that the M16A2 model is a very influential model in the M16 family and is still in use in various military forces. We will continue to look at other members of the M16 family in this post.

M16A4: This rifle is the fourth generation rifle in the M16 series. One of the main differences between this model and the models we've have already studied so far is that the carrying handle on this model is detachable. What the designers did was put picatinny rails on the rifle and also on the hand guards. The carrying handle is attached to the picatinny rail on top and can be removed and replaced with other accessories, such as a reflex sight, night vision device etc. In addition, other accessories may also be attached to the other rail mounts, such as a laser, vertical grip, flash light etc.

The M16A4 rifle. Click on image to enlarge. Public Domain Image.

In the above image, note that the carrying handle has been replaced by a telescopic sight called an ACOG (Advanced Combat Optical Gunsight) and the rifle has an additional vertical grip attached to the hand guard in front. The M16A4 has the same firing modes as the M16A2 (i.e. single shot and 3 round burst) and also retains a bunch of other features from it.

The US Marines were the first to adopt this rifle model and are in the process of phasing out their existing M16A2 rifles with the M16A4. It is also used by some other countries' military forces around the world, such as Thailand, Turkey etc.

M4 Carbine: During the Vietnam war, Colt developed a carbine version of the M16A1, called the CAR-15. Around 1988, there came a need for another carbine design and Colt based it off the influential M16A2 design. The M4 carbine features a shorter 14.5 inch barrel and a telescoping stock. Therefore, it is more compact than the M16A2. It also borrows from the M16A4, by incorporating the rails and the detachable carrying handle, therefore allowing it to accept a wide variety of accessories.

US Soldier carrying a M4 with accessories attached. Click on image to enlarge. Public domain image

Due to its shortened barrel, the ballistic performance of the bullets is slightly worse than the M16A2. However, the smaller length makes it more suitable for close quarter battle. The M4 carbine was first selected for use in 1994, by the US Army, initially to replace the M9 pistol and the M3/M3A1 submachine gun. Later on, they began to replace the M16A2 rifles as well and the US Marines also adopted it for use by officers. Other branches of the military started using it as well and it is also used by other countries around the world.

One variant of the M4 is the M4A1 carbine, which is used by US Special Operations units, such as the Navy SEALs, Army Special Forces, Marines Force Recon, USAF Para-rescue etc. The difference is that while the M4 is capable of single shot and three round burst firing modes, the M4A1 is capable of single shot and fully automatic firing modes.

AR-15: The original prototype of the first M16 model was called the AR-15 (after the company Armalite, which was the original designer of this rifle family). However, after Colt bought the design, they called their model the M16 and made a civilian model of the design in 1963, which they named the AR-15. In this discussion, we will only talk about the civilian models released by Colt and other manufacturers, as few examples of the original Armalite design exist. The AR-15 was designed for civilian sales and while it does have a resemblance to other members of the M16 family, there are some very significant differences. The first major difference is that the AR-15 only has one firing mode (semiautomatic mode, which means you have to pull the trigger each time to shoot a new cartridge). Therefore, it is NOT an assault rifle, since it is incapable of switching firing modes. While the external appearance of an AR-15 is almost identical to a fully automatic M16 family model, the internals are very different. The hammer and trigger are of a different design and the bolt carrier and lower receiver are differently shaped that they cannot be interchanged with a M16 mechanism. This is done to satisfy United States firearm laws that semi-automatic weapons cannot be easily converted to fully-automatic weapons.

Colt AR-15 A3 Carbine Model. Click on image to enlarge.

There are multiple models of AR-15, resembling various other variants of the M16 family. While Colt officially holds the trademark to the term "AR-15", clones are made by many other manufacturers and they are unofficially all referred to as "AR-15". Many of these clones are designed to fire other calibers of ammunition, ranging from small pistol cartridges, to many different rifle calibers and even shotgun shells.

These are only some of the popular variants of the M16 family. There are other international variants that we will study in our next post.

Sunday, October 27, 2013

The M16 Family - I

Many months ago, we had explored the differences between various members of the AK family (e.g.) AK-47, AKM, AK-74, AK-101 etc. In today's post, we will explore some of the popular members of the M16 family and discuss the differences between them. We will study the differences in multiple posts, as there are quite a few variants with major differences.

M16: This is the first operational version of the rifle and was only adopted by the US Air Force initially. Among its distinctive features are a triangular shaped forward hand guard, no cleaning compartment in the stock (as Colt famously declared that this rifle was so advanced that it didn't need one), no forward assist lever and a duckbill shaped flash suppressor at the muzzle. The original version was issued with a 20 round magazine. It is capable of selecting firing modes and can fire in single-shot as well as fully automatic modes. The barrel has a rifling twist of 1 turn in 12 inches.

Original M16 rifle. Click on image to enlarge. Public domain image.

In the above image, we see an original M16 rifle. This variant was adopted by the US Air Force, which continued to use this model until 2001 before switching to the M16A2 variant. It was also used by some other military forces, notably the British SAS.

M16A1: This is the variant that was first accepted by the US Army. Soon after the original M16 was ordered by the US Air Force, the Army got in the act and asked for a model with a few changes to it, notably, the addition of a forward assist lever, in case the cartridge did not properly seat in the chamber. Colt and the US Air Force believed that this change was unnecessary, over-complicated the weapon and increased its cost by $4.50. Hence, the Air Force got the M16 variant and the Army got the M16A1 variant., which has the forward assist lever. One more difference is that the duckbill flash suppressor was found to pick up twigs and leaves in jungle conditions and was replaced by a bird-cage style flash suppressor. This variant retains the same triangular forward hand guards, selectable firing modes (single-shot and fully automatic) and rifling twist of the original M16.

The M16A1 rifle. Note the bird-cage flash hider in front of the muzzle and the presence of a forward assist lever.

Early versions of the M16A1 were issued with no cleaning kits and without a chrome lined chamber. This led to a number of jamming issues early on and investigations were made to determine why this was happening. A change in the ammunition formula was found to be the cause, as the new ammunition left more residue in the rifle. Since the rifle was issued without a cleaning kit, soldiers could not properly maintain their weapons and this led to jamming problems in the field. Immediately after the cause was determined, the rifle was changed to include a cleaning kit, stored in a compartment in the stock. The barrel. bolt and chamber were also chromed to resist corrosion. In 1970, the magazine was changed from 20 round capacity to a 30 round capacity, as can be seen in the image above.

After its initial reliability problems were solved, the M16A1 variant became adopted by the US Army and the Marines, as well as other military forces around the world, such as Argentina, Australia, Thailand etc. It is still used by some military forces.

M16A2: This is a very influential version of the M16 family and has a number of differences from the M16A1. Most of the changes were added because of the US Marines. The Marines found that in the Vietnam war, many inexperienced men would put the rifle into fully automatic mode and end up emptying their magazines into the bushes without hitting a single enemy. Hence, they asked for the automatic firing mode to be removed and a three-round burst mode to be added instead. This makes the M16A2 variant capable of firing in single-shot and three round bursts only. Also, NATO forces wanted to use a more powerful version of the 5.56x45 mm. cartridge (the SS109 cartridge). However, the newer cartridge needed the rifling twist of the barrel to be changed, in order to maintain bullet stability in the air. Hence, the M16A2 features a barrel with a twist rate of 1 turn in 7 inches (compared to 1 turn in 12 inches for the earlier models) to work with NATO standard cartridges. The barrel thickness was also increased as the US Marines wanted a stronger barrel to resist bending in the field and not overheat as quickly.

The M16A2 rifle. Click on image to enlarge. Public domain image.

There are also many other major changes. For instance, the material of the buttstock plastic is different and 10 times stronger than the original. The shape of the forward hand guards is round instead of triangular and the two handguard pieces are symmetrical (meaning that either half can fit as the left or right side hand guard). This enables the rifle to be held more easily by smaller hands and the symmetrical hand guards make production easier, as there is no longer a need to manufacture separate left-side and right-side hand guards. The shape of the pistol grip is also different - this version has a notch added to support the middle finger and it has more texture to enhance the grip. Because this rifle is designed to fire the NATO SS109 cartridge, the rear sights are also changed to match this new cartridge's ballistics. Also, the flash suppressor is modified and closed at the bottom, so that it will not kick up dust or snow when fired from the prone position.

This variant was initially adopted by the US Marines and then by the US Army, followed by the other branches of the US military and other military forces around the world. It is still being used by many military forces around the world.

M16A3: This is a variant of the M16A2 model that came out at around the same time as the M16A2. It was produced in small quantities and designed for US Navy SEALS and the Seabee units. The main difference is that while the M16A2 can only fire in single-shot and three-round bursts, the M16A3 can fire in single-shot and fully automatic modes. Special forces are trained to not waste ammunition and hence, this variant allows fully automatic fire.

In the next post, we will study some more variants of the M16 family.

Thursday, October 17, 2013

Fanning a Revolver

Fanning a revolver is a technique often used by trick shooters to increase the rate of fire of single action revolvers. In a single action revolver model (such as the legendary Colt Single Action Army revolver), pulling the hammer back by hand cocks the revolver and also turns the cylinder to the next chamber. Pulling the trigger releases the hammer. Therefore, to fire the revolver multiple times, the user must pull the hammer back first, then pull the trigger to fire it, then pull the hammer back again, pull the trigger again and so on, until the revolver is empty. However, it is also possible to hold the trigger down with one hand and then pull back on the hammer with the other hand and release it and keep doing this rapidly. Each time the hammer is released, it falls and detonates the cartridge in the chamber and each time it is pulled back, the hammer cocks and the cylinder rotates to the next chamber. Since the trigger is held down, the hammer cocks but does not lock back and falls back immediately after it is released. Therefore, the rate of fire is down to as fast as the user can pull the hammer back. In order to do this rapidly, the user usually uses a fanning motion with the cocking hand.

The video above demonstrates this technique. Due to the rates of fire that can be achieved by this technique, it is used by trick shooters and fast-draw competitors.

However, it must be noted that this technique may also damage a revolver's stop mechanism, especially when done very rapidly. One more point to be noted is that it isn't very good for shooting accuracy. There are only a few people that can shoot reasonably accurately with this method. That is one more reason why it is seen in trick shooting shows and not used very much by ordinary people.

Thanks to Hollywood movies, some people are under the impression that this was a standard technique used by cowboys in the 1850s. For an example, here's a scene from the classic western movie "Shane".

The technique of fanning a revolver was definitely known during that era, but the reality is that most real gunfighters did not use this technique in real fights, because of concerns of accuracy. What did real gunfighters think of this technique then? The following quotes are by one of the most famous gunfighters, Mr. Wyatt Earp, taken from an interview he gave later in life:

"In all my life as a frontier peace officer, I did not know of a really proficient gunfighter who had anything but contempt for the gun-fanner, or the man who literally shot from the hip"

"From personal experience and from numerous six-gun battles which I witnessed, I can only support the opinion advanced by the men who gave me my most valuable instruction in fast and accurate shooting, which was that the gun-fanner and the hip-shooter stood small chance to live against a a man who, as old Jack Gallagher always put it, took his time and pulled the trigger once."

"A skilled gun-fanner could fire five shots from a forty-five so rapidly that the individual reports were indistinguishable, but what could happen to him in a gunfight was pretty close to murder."

"Hickok (“Wild Bill” Hickok) knew all the fancy tricks and was as good as the best at that sort of gunplay, but when he had serious business in hand, a man to get, the acid test of marksmanship, I doubt if he employed them. At least, he told me that he did not. I have seen him in action and I never saw him fan a gun, shoot from the hip, or try to fire two pistols simultaneously. Neither have I ever heard a reliable old-timer tell of any trick-shooting employed by Hickok when fast, straight-shooting meant life or death."

These quotes and others are found in an authorized biography, "Wyatt Earp: Frontier Marshall" by Stuart N. Lake, where he gave a personal interview to the author about his life experiences.

Monday, October 14, 2013

Firing Different Sized Cartridges?

After all that stuff we read about headspacing, in the last couple of posts, let's look at a tangential topic here. In the image below, we have three kinds of cartridges, all of .22 caliber, but of different lengths:

From left to right, .22 CB, .22 Short and .22 Long Rifle (LR) cartridges.
Public domain image.

The three cartridges in question are (from left to right), .22 CB, .22 Short and .22 Long Rifle (popularly known as .22 LR). Now imagine that you have a firearm that is designed to shoot .22 LR. Will it be able to shoot the other cartridges?

To answer this question, we must first note that these are rimmed cartridges, i.e. the rims of the cartridges are wider than the body of the cartridges. Also note that although the overall lengths of the cartridges are different, the diameter of the cartridge cases and bullets are identical. Also, the sizes of the rims in all three cases are identical.

Now, when we first started talking about headspacing two days ago, recall how the headspace for rimmed cartridges is measured.

Click on image to enlarge.

That's right, for rimmed cartridges, the headspace is measured as the width of the rim. Therefore, a firearm that can fit a .22 LR cartridge (the longest of the three) can also comfortably fit a .22 short, a .22 Long and a .22 CB. Since all these cartridges have the same rim diameter and rim width, they also headspace correctly. This means that a .22 LR firearm can fire these without the fear of case separation occurring.

Of course, a few caveats must be noted here. The first is that of the .22 Short, .22 Long and .22 LR, they were all originally designed to use the same propellant, black powder, with the .22 LR having the most quantity in the cartridge (the .22 CB is even more low powered than these three). Therefore, a firearm designed for .22 LR is strong enough to handle the pressures generated by the other cartridges. Also, since the .22 LR is the longest of the four cartridges, the other three can fit in the chamber. Since all four of these are rimfire cartridges, the same firing mechanism can be used for all of them. However, it must be noted that just because a firearm designed for .22 LR can be fired with any of these 4 cartridges does not mean it can function after that. For instance, cartridges may have to be manually fed in one at a time, because a .22 LR magazine may not feed the other cartridges properly due to the different lengths of the cartridges. Also, the recoil forces generated by the smaller cartridges may not be enough to cycle the action of a firearm designed for .22 LR properly. Therefore, depending on the type of firearm and its action, the user may have to manually extract and feed smaller cartridges. The sights will also have to be adjusted, since the smaller cartridges have less power and shoot at lower velocities. Hence, while it is possible to safely fire .22 CB, .22 Short, .22 Long and .22 LR out of a firearm designed for .22 LR, there are many reasons why people do not always do so.

One more major caveat -- there are other so-called cartridges in .22 caliber, for instance, the .22 Magnum (a.k.a. .22 WMR or .22 Winchester Magnum Rifle). This cartridge cannot and should not be fired from a rifle designed for .22 LR. For one thing, the two cartridges are actually of different diameters and lengths. On top of that, .22 WMR uses much stronger propellant that .22 LR and therefore generates higher pressures (which is the reason why they increased the diameter and length of the .22 WMR cartridge, so it cannot fit into a .22 LR firearm chamber, otherwise it could be a dangerous situation because the .22 LR firearm may not be able to handle the higher pressure). A .22 LR cartridge can fit in the chamber of a firearm designed for .22 WMR, but since the cartridge is of smaller diameter, when the cartridge is fired, it may split in the chamber and stick to it.

Therefore, it is always a very good idea to always know the exact ammunition type of a firearm.

Sunday, October 13, 2013

Headspacing - II

In our last post, we looked into the subject of "headspacing", we will continue to study our subject in this post. As was suggested in our last post, headspace is the distance between the bolt face and a point in the chamber that prevents further forward movement of a cartridge. Depending on the firearm and the shape of the cartridge, this distance can be different for different types, as the figure below shows:

Click on image to enlarge.
Image is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported by user Amendola90 at

Now we will look into what happens if the headspacing is not correct. There are two scenarios we must consider here. The first is excessive headspacing, where there is extra space between the bolt face and the cartridge in the chamber. The second is insufficient headspacing, where there is too little space between the bolt and the cartridge.

What if there is excessive headspacing? In this scenario, when the firing pin hits the cartridge, it will move forward into the chamber before detonating. When the propellant explodes, the walls of the cartridge will expand due to heat and firmly stick to the walls of the chamber, preventing rearward motion of the cartridge. However, the thicker base of the cartridge will move backwards, because there is now a gap between it and the bolt face and this will cause the walls of the cartridge to stretch. If the stretching is too much, the walls of the cartridge could rupture and release hot gases into the action and also potentially spray case fragments out from the action of the firearm, which could be hazardous to the shooter or people standing next to him.

Well, what if there is insufficient headspacing in the chamber? In this scenario, the back of the cartridge will stick out of it and the user will not be able to close the bolt fully on the loaded cartridge. The user will not be able to properly operate the firearm if this happens. If the user were to force the bolt to close on the cartridge, this pushes the bullet tightly into the case neck and if the firearm is fired, this will cause excessive pressure to build up inside it, leading to hot gases coming out of the cartridge's primer pocket with similar results as excessive spacing. In worst case scenarios, the excess pressure could cause the action to rupture and cause damage to the gun and its user.

So, how do we determine that a firearm has proper headspacing? We can do that by using a set of gauges, called headspacing gauges. These are measuring instruments that are precisely machined to the SAAMI or CIP or military standards of a cartridge caliber. Typically, these are made of heat-treated steel and are machined to tolerances below 0.001 inches or so. They are made for various calibers by several reputable commercial companies at fairly reasonable prices. Typically, there is a "Go" gauge, a "No-go" gauge and (for military specification rifles), a "Field" gauge.

Headspacing gauges. Top is a "No-go" gauge and bottom is a "Go" gauge

The "Go" Gauge: A firearm must be able to close the bolt with no resistance at all, when a "Go" gauge is inserted into the chamber. This signifies that the firearm is able to meet the minimum length specification for the cartridge. If the bolt does not close on the "Go" gauge, this means that the firearm has insufficient headspacing and may be dangerous to fire, even if the user manages to force standard cartridges to fit in the chamber. Sometimes, the cause of this may be a dirty chamber or bolt face, because the accumulated dirt may be thick enough to prevent the bolt from closing on the gauge. However, if the firearm is clean and the bolt still does not close on the "Go" gauge, it must be taken to a competent gunsmith for adjustments.

If a firearm successfully closes on a "Go" gauge, it means that the firearm at least has sufficient headspace, but it may still have excessive headspace. That can be determined with our next gauge.

The "No-go" Gauge: A new (or overhauled) firearm must not be able to close on a "No-go" gauge. If the bolt closes successfully on a "No-go" gauge, this means the firearm has excessive headspace and there is a risk of cartridge cases rupturing inside the chamber. If the firearm is new or recently repaired, that means it should be returned to the manufacturer immediately.

A used firearm may be able to close on a "No-go" gauge, due to wear of the bolt and chamber surfaces, but this means that it should probably go to a gunsmith for repair soon and it may be possible to fire new factory ammunition in it until then, but reloaded ammunition is probably a bad idea and the firearm may malfunction on slightly out-of-spec cartridges. Here's where the test with the third gauge comes in (especially for firearms built to military specifications).

The "Field" Gauge: The bolt of any firearm, whether old or new, should not be able to close on a "Field" gauge. A bolt that closes on "no-go", but not on a "field" gauge, may be considered close to being unsafe, but may work on new cartridges (and should be sent to a gunsmith soon for possible re-headspacing). However, if the bolt closes on a "field" gauge as well, then it is definitely not safe to fire and should be sent for repairs immediately (or mounted on a wall as a decorative piece!).

Some calibers have a fourth gauge called a "Field II" gauge, for which the bolt should never lock on. This type of gauge is only used by some rifles (for example, Colt uses it to reject M-16 rifles).

It must be noted that gauges are usually manufactured to either SAAMI, CIP or military standards and therefore may have different dimensions, even for the same caliber cartridge. Therefore, it may be possible that a rifle manufactured to NATO specifications, may lock on a "No-go" gauge built to SAAMI specifications, but correctly not lock on a "No-go" gauge built to NATO specifications. This is because military weapons are generally designed to operate with wider tolerances and military ammunition cases are generally thicker than commercial ammunition and can tolerate more stretching without rupturing. Therefore, a military firearm may fail the test using SAAMI gauges, but still be deemed somewhat safe to fire per the military specification gauges. However, if it passes even with using SAAMI gauges, that means it is very likely to work correctly.

Go, No-go and Field gauges are available from many firearm supply stores and cost about $25 to $50 per gauge or about $70 to $140 per set.

Saturday, October 12, 2013

Headspacing - I

It has been a while since the last article. Today, we will study an important concept called "Headspacing". This will be a two-part post.

The term "headspacing" is defined as the distance between the face of the bolt and a point in the chamber that prevents further forward movement of a cartridge.

Click on image to enlarge. Public domain image.

In the above pictures, we have a .45 ACP cartridge loaded into a chamber. The cartridge case is a bit larger than the bullet and the chamber is shaped so that it fits the case correctly. Of course, depending on the shape of the cartridge, the headspacing could be different for different firearms.

For instance, some of the earliest metallic cartridges were rimmed. This means, they have a rim at the base of the cartridge that is larger than the diameter of the cartridge case. When this type of cartridge is pushed into a firearm's chamber, the rim positions the cartridge correctly and prevents it from slipping too far into the chamber. Therefore, for a rimmed cartridge, the proper headspacing should be the width of the rim.

Headspacing of a rimmed cartridge. Click on image to enlarge.

The most popular cartridge today, the .22 Long Rifle rimfire cartridge is an example of a rimmed cartridge.

However, it must be noted that most modern cartridges are rimless (i.e.) the diameter of the rim is the same or smaller than the diameter of the case body. Modern cartridges have other ways to ensure that the bullet seats in the chamber correctly. For example, for most pistol cartridges, the case diameter is slightly larger than the bullet and the chamber has a shoulder that the case mouth rests against.

Headspacing on a .45 ACP rimless cartridge. Click on image to enlarge.

In the image above, we see a .45 ACP rimless cartridge seated in a chamber. The case mouth is larger than the bullet diameter and rests against the front of the chamber, thereby correctly seating the cartridge.

Other rimless cartridges, such as bottle-necked cartridges (which are mostly used by rifles), the shape of the firearm's chamber is correspondingly tapered to achieve proper headspacing.

Headspacing on a bottlenecked rimless cartridge. Click on image to enlarge.

In the above image, we see that the chamber is tapered to accommodate the cartridge and the headspacing is the distance from the bolt face to the tapered section.

In the case of belted cartridges (such as the hunting cartridge, Holland & Holland .300 Magnum), the chamber is shaped to seat the forward face of the belt.

Headspacing on a belted cartridge. Click on image to enlarge.

When the H&H .300 Magnum was first being developed, it was difficult to provide proper headspacing for a cartridge with a shallow shoulder design. The solution was to add a belt around the cartridge body. This is similar in function to the rim of a rimmed cartridge, but gave a long enough surface for the cartridges to fit side-by-side in a magazine, without risk of interference during the feed stroke. This idea was later copied by other magnum rifle cartridges as well.

We will study the importance of proper headspacing in the next post.

Sunday, September 15, 2013

Unusual Firearms: Key Guns

In our last article about unusual firearms, we looked at the Greener police shotgun. In today's post, we will look at a very unusual class of firearms, a combination of a key and a gun, the so-called Key Gun.

Key guns were apparently used in the 17th and 18th century, but they are pretty rare. They were apparently intended to be used by jailers for self-defense purposes, when they were making their daily inspections of the prison cells. The idea being that the jailer could use the same object to open the cell door and also defend himself, in case the prisoner inside tried to escape.

Key guns were initially incredibly primitive devices. The example above is merely a tube sealed on one end, with a touch-hole on top. Note the lack of any firing mechanism. The jailer would have carried a lit cigarette or cigar in his mouth. To discharge this weapon, the jailer would touch his cigar on the touch-hole and light the powder within the key.

Some other examples had actual firing mechanisms. For instance, we have a model that uses a matchlock firing mechanism, one using a flintlock and another one using percussion cap technology.

Click on images to enlarge.

Whether these weapons were actually practical or not is a completely different matter. These are all small-caliber and short range firearms with low stopping-power and it isn't quite clear how usable one of these is once the jailer has started turning the key, because the gun can no longer point at the prisoner and the jailer can't put his finger on the trigger while turning the key. No wonder then that these weren't very popular.

Monday, August 26, 2013

Corrosive Ammunition

Many months ago, we talked about the development of the percussion lock. This was where the idea of striking a shock-sensitive substance with a hammer to ignite the main charge of propellant was originally developed. In that article, we had mentioned that mercury fulminate was originally used as the primer and was later replaced by potassium chlorate. This idea of using a shock sensitive priming material is still used in today's centerfire cartridges. However, there were some issues with using such primer materials and we'll study about them in this post.

In our discussion about the percussion lock previously, we'd mentioned that the inventor (the Rev. Alexander Forsyth) had used mercury fulminates to set off the main charge. Mercury fulminates continued to be used in priming caps for early centerfire cartridges as well, into the end of the 19th century. However, when people started to switch to using smokeless powders, they began to discover the downsides of mercury fulminate. One of the issues was that mercury fulminate tended to degrade when kept in storage. This was not really an issue when using black powder cartridges, because black powder ignites a lot easier than smokeless powders. However, once people started to switch to smokeless powders for extra power, they found that keeping the cartridges in storage would cause the mercury fulminate primers to degrade so much that they could not reliably ignite the smokeless powder, causing misfires and hang fires. One more problem with mercury fulminates was that in conjunction with smokeless powders, it tended to form copper and zinc amalgams in the brass cases of cartridges, thereby making them unsuitable for reloading.

Due to this, the US Army switched to using potassium chlorate primers in 1898. Some other manufacturers used sodium chlorate instead. While these primers did not degrade as much as mercury fulminate, there were some other problems that came with them. When fired, these primers would decompose and leave a residue of potassium chloride (or sodium chloride) behind in the barrel. Those of you who remember your chemistry lessons in school might remember that sodium chloride is the scientific name for common salt. Potassium chloride is also another corrosive salt. These salts are highly hygroscopic (i.e.) they tend to attract water, especially when in humid conditions. Guess what happens when you have salt and water applied to an iron or steel surface -- that's right, it rusts. Therefore, if the barrel and action are not cleaned after firing such cartridges, there's a good chance that they could rust soon after. Swabbing the surfaces with oil will not prevent these salts from attracting water and rusting the metal.

As a result of this, primers using non-corrosive chemicals were developed in the 1920s, but these were generally used in civilian ammunition only, as the early non-corrosive primers did not last as well in storage as corrosive primers. Due to this, military ammunition tended to use corrosive primers and this was indeed the case for US military ammunition until the 1950s or so. Some other countries (e.g. former Soviet Union, China, Yugoslavia, Bulgaria etc.) continued to use corrosive primers in their cartridges for much longer than this, well into the 1970s and 1980s. Therefore, depending on the source and the age of the ammunition, the user must be wary lest the ammunition is corrosive.

So how does a user ensure that his firearm doesn't rust after using corrosive ammunition. The good news is that this is fairly easy to handle. It turns out that these corrosive salts dissolve in water. Therefore, cleaning the firearm thoroughly using water or a water based lubricant should do the trick. Some people use hot soapy water, others use plain water, still others swear by windex glass cleaner (which is largely water based). After washing off the residue, the firearm should then be dried, then cleaned with normal bore cleaning solution and oiled, as per the normal cleaning procedures.

The firearm should be thoroughly cleaned as soon as possible after firing the corrosive ammunition, to ensure that the corrosive chemicals are removed before they can damage the firearm. While this may seem like a bit of extra work, it is well worth it because there is no way to restore a barrel or chamber back to perfect condition, once it has started to rust. Therefore, the user should go through the extra effort if the ammunition is suspected to use corrosive primers.

As it turns out, the price of surplus ammunition using corrosive primers is often much lower than other types and it is also widely available in the market. So how does a user identify if the ammunition is corrosive or not? One way is by looking at the markings on the cartridges and the manufacturer of the ammunition. For instance, if it is surplus ammunition from certain countries such as the former Soviet Union, Yugoslavia or China, there is a good chance it uses corrosive primers, especially if it is manufactured before the 1980s. US-made ammunition has markings that can give a good clue as to whether the primers are corrosive or not. In case of doubt, there's an easy way to find this out. The user can take a cartridge, pull out the bullet from the front and empty out the powder from the cartridge and only leave the primer behind. Then. the user fires the empty cartridge onto a mild steel plate from a distance of about 1 inch from the muzzle, so that the primer chemicals are deposited on the plate. The user also fires another primer that is known to be non-corrosive onto another section of the steel plate. After firing the two cartridges, the user cleans the firearm as detailed in the procedure above, in case the suspect ammo is indeed corrosive. Then the user simply keeps the steel plate in a warm humid area for a few days. If the section where the suspect primer is fired over shows substantial rusting, then it uses corrosive chemicals.

Another way is to use bright common nails (which are nails made of mild steel with no coating) and pop a primers over one of these nails. If the nail rusts within a couple of days, then the primer is corrosive. The following video shows how this is done, using simple household tools:

Interestingly, the box of suspect ammunition actually says that it is non-corrosive on the box, but it turns out to be corrosive after all. Happy viewing!

Monday, August 19, 2013

What the heck is an "Arshin"?

Imagine you are now the proud owner of a classic Russian Mosin-Nagant M-91 rifle and are excited to try it out for the first time. So you take it out to the range, adjust the iron sights for a target 400 meters away and shoot at it. Upon shooting a few times, you examine the target and notice that you're not hitting where you're aiming at. Is there something wrong with the rifle? Actually, the answer may have to do with your misunderstanding about how the sight works.

A Konovalov type Mosin-Nagant adjustable iron sight.

In the above image, we see a Mosin-Nagant rifle sight called the Konovalov type. This sight acts as both a  tangent sight (for shorter ranges, marked as 4-12) and a ladder sight (for longer ranges, marked as 13-32). Note that the sight is sort of curved, as seen in the first image. Older Mosin Nagants have a flat shaped sight using the same idea.

The mistake that some people make is assume that these settings are in meters (e.g. 4 = 400 meters, 6 = 600 meters etc.) For Mosin-Nagants manufactured before 1930, this is not true -- in fact, these are calibrated in a unit called "Arshin" (plural: "Arshins" in English, "Arshiny" in Russian). So what the heck is an "Arshin" then?

To answer this question, we must go back to 16th century Russia, where this unit of length first originated. This unit was the Russian equivalent of the English "yard" measurement. Its actual length varied over the years, until Peter the Great standardized it in the 18th century to be about 27.95 inches long (or about 71.1 cm. or 0.78 yards). This continued to be how distances were measured in Russia until some time in 1925, when the Soviet Union officially adopted the metric system throughout the country. Konovalov type sights calibrated in arshins continued to be manufactured for some years after, until 1929.

Therefore, with older Mosin-Nagant rifles built before 1930, the sights were actually calibrated in arshins. Hence, when the slider is pushed to 4, the sights are set to aim at a distance of 400 arshins, not 400 meters. 400 arshins is approximately 285 meters, which explains why the rifle might not be shooting where the user expects it to!

Edit: The editor is indebted to Mr. Bernard Samartsev for his comments and corrections to the original article noted below.

Tuesday, August 13, 2013

The Greener Police Shotgun

The topic of today's study will be an unusual firearm, the Greener police shotgun.

The history of this unusual firearm dates back to shortly after World War I, when the British ruled over very large portions of the planet and the sun never set on the British empire. In several colonies around the globe, the British set up police forces employing locals to handle ordinary law and order issues, with British army garrisons to put down major rebellions and uprisings. There came a need to equip the local police forces of countries like Egypt, India, Hong Kong etc., with weapons to put down riots and jail escape attempts, without the need to involve the local army garrison. Therefore, the British government issued a specification for a new firearm for these police forces.

The requirements of this new firearm type were a bit unusual. First, many of these police forces were not well trained or educated, therefore the firearms had to be extremely simple, sturdy and reliable. They were expected to need minimal maintenance. Since there was a chance that the guns could be used against the British troops themselves, the guns had to be short-range weapons and single-shot only. Another request was that the cartridges used for these firearms should not be easily available. That way, if the police forces decided to rebel themselves, the British garrison could easily take them on.

Greener police shotgun. Click on image to enlarge.

With these requirements in mind, the firm of W.W. Greener, a well known manufacturer of firearms from Birmingham, UK, came up with the Greener police shotgun. The action chosen for this firearm was the Greener improved Martini action that we studied a couple of years ago. This reliable action was known for its simplicity and ruggedness. It was in the Martini-Henry rifle since 1871 and the Martini-Henry rifle was already used by many local militaries, which meant that many locals would be familiar with it. In addition, the barrel, springs and action were made of heavy-duty steel for extra strength and durability. The wood stock extended all the way to the end of the barrel, to prevent damage to the barrel. In addition, note the solid steel nose cap at the muzzle end of the barrel in the picture above. This cap served as extra protection for the end of the muzzle, so even if the gun was placed vertically with the muzzle-end on the floor, the steel cap kept the barrel about 1/4" off the floor. In addition, a bayonet could be attached to the steel cap. The butt-end of the stock also had a steel plate at the end, so it could be used as a club. The stock also had a compartment to store cleaning tools. The barrel of this shotgun had no rifling, so it could only be used as a short range weapon and since it used the Martini action, the user would have to manually unload and reload a new cartridge, each time he desired to fire it. The cartridge that this shotgun was designed to fire was a proprietary 14-gauge shell manufactured by Kynoch Ltd.

The original Mark-I model of this shotgun was released in 1921, mainly to colonial police forces in Egypt. However, it was soon discovered that unauthorized users could use a smaller commonly available 16-gauge cartridge in this gun and stuff the extra space with paper. In response to this, Greener released the Mark-III model shotgun, which had some improvements to prevent this:

New improved cartridge for the Greener Police Shotgun Mark III

In this newer model, the shotgun chamber was altered to take an unusual shaped cartridge. The base of the cartridge was the same diameter as a 12 gauge cartridge, but the front of it was narrowed down to 14 gauge. With an unusual bottle-necked cartridge shape like this, this cartridge could not be used with any other firearm.

In addition, the striker of the shotgun was also modified so that it could only be used with these unusual cartridges. Instead of a normal needle shaped striker, the new striker on this shotgun was shaped like a trident, with the outer two prongs longer than the middle prong. Note that the base of the new cartridge has a deep circular groove around the primer cap. The reason for this groove is so that the two outer prongs fit into the groove and the shorter middle prong can strike the primer of the cartridge. Therefore, the Mark-III shotgun could not use any other ammunition, except for this type of cartridge. If any other cartridge was used, the two longer outer prongs of the striker would strike the base of the cartridge first and prevent the shorter middle prong from striking the primer.

The end result of this was a cartridge that could not be used on any other firearm and a shotgun that could only fire a particular cartridge type. The British authorities were very careful to issue these cartridges in very limited numbers (about two or three per person). Therefore, if criminals stole these weapons or if the local government revolted, these guns would be useful only while the ammunition was available for them.

A lot of these shotguns were issued to colonial police forces in Egypt, Malaya, Hong Kong etc. Some of them were imported into the US in the 1930s, to be used in prisons. Greener continued to manufacture these shotguns even after British colonial rule ended in many parts of the world, until about 1975 or so. Used examples can be found on sale even today.

Tuesday, July 23, 2013

The Boys Anti-tank Rifle

In our last post, we studied the world's first anti-tank rifle, the Mauser T-Gewehr M1918, which was invented by the Germans. Today, we will study the history of another anti-tank rifle, the British Boys Anti-tank Rifle.

In the last post, we studied that the Mauser T-Gewehr was invented by the Germans because they didn't have any tanks of their own during World War I and had to come up with some solution to counter British and French tanks. Although tank armor had become thick enough to resist the Mauser by the end of World War I, the idea of an anti-tank rifle did not go away.

In 1934, the British decided to design a weapon that could penetrate light armor. The project was originally called Stanchion and was given to the Royal Small Arms Factory of Enfield, Middlesex, England to design. The chief designer of this project was a Captain H.C. Boys.

Captain Boys intended the rifle to be a bolt-action large bore rifle, capable of penetrating light armor, but light enough to be carried by a single person. He looked at the existing rifle cartridges of the day. The 30-06 and the .303 cartridges were found to be too weak (even the armor-piercing variants). The US made Browning .50 BMG cartridge was found to have some potential, because it could penetrate 3/4" armor at 100 yards, but they wanted something a bit more powerful than the .50 caliber cartridge. Therefore, they started with a Browning .50 caliber cartridge case, widened the case's neck to accept a .55 caliber steel-core bullet and added a belt around the cartridge base for proper headspacing (the idea of adding a belt on the base of a magnum cartridge was a British invention by Holland & Holland in 1910 for their larger hunting rifles firing the powerful .375 H&H magnum cartridges). This new cartridge weighed 946 grains (64 gm.) and had a velocity of 2495 feet/sec, delivering 17726 ft-lbf (24033 joules) of energy. By comparison, the .30-06 cartridge (all variants) delivers somewhere between 2800 to 3000 ft-lbf of energy. The job of manufacturing the new .55 caliber cartridge was given to Kynoch Ltd., a well known manufacturer of cartridges in England.

With the cartridge designed, the next goal was to design a rifle around this cartridge. It was simply a bolt-action design with a 5-round magazine, weighed about 35 lbs. (16 kg.) and was about 5 feet 2 inches (1.575 meters) long. The magazine was top-mounted and therefore, the sights were offset to the left to accommodate this. Tragically, the designer of this rifle, Captain Boys, died a few weeks before the rifle went into production in November 1937. Hence, the rifle was renamed as the Boys Anti-tank Rifle in his honor.

The Boys Anti-tank Rifle Mark I. Click on image to enlarge. Public Domain Image.

The rifle was manufactured in three variants. The Mark I variant (as shown in the image above) was the original design manufactured by the Royal Small Arms Factory in Enfield. Notice the round muzzle brake and the T-shaped bipod The Mark I* was given to the Canadian company, John Inglis & Co.  to manufacture and this variant had a V-shaped bipod and flat muzzle brake. The Mark II Airborne variant was designed to be carried by paratroopers and had a shorter muzzle.

When the Boys rifle was delivered, it was not effective against German panzers since the very beginning of World War II. While the bullet fired by this rifle could penetrate through mild steel plate of 23.2 mm. thickness (almost 1 inch thick) at about 90 meters (100 yards) range, the frontal armor of the German tanks was thicker and harder than this and therefore the rifle didn't fare very well against them. However, they proved to be more effective against armored cars and Soviet and Japanese light tanks. The Finns used them against Soviet tanks in 1940. The original steel-cored bullet was later replaced by a tungsten-core bullet (the .55 Mark II cartridge) in an attempt to improve its effectiveness. Despite the cushioned butt pad on the stock, the recoil from this weapon was terrific and often ended up bruising the operator's shoulder, which made soldiers very reluctant to fire it unless it was mounted to a support. This weapon did find some success with the British commandos of World War II (the Desert Rats), who mounted it to the top of their trucks and Bren carriers, when they went on raids in the desert.

Since the rifle had such a heavy recoil, an adapter kit was designed to be used by this rifle for training purposes.

What the adapter kit did was allow the user to mount a smaller .22 caliber rifle to the side of the Boys rifle and fire that via the trigger of the Boys rifle. This allowed for users to learn basic sighting techniques, without having them to bear the force of firing the Boys rifle during training sessions.

The Walt Disney Company was also commissioned to produce a training video for this gun during World War II:

Yes, that is a Disney cartoon animation at the beginning of the first video.

While the Boys rifle was largely ineffective in its original role of stopping German tanks, it was more effective against lighter skinned vehicles, early Soviet and Japanese tanks and armored vehicles. US Marines used it against Japanese bunkers as well. By the end of World War II, this rifle was seen as obsolete and was replaced by bazooka type anti-tank weapons. However, they were still used in the Korean war and in the Philippines until 1960 or so. One was even used in the 1960s by the IRA to disable a British Navy Patrol Boat HMS Brave Borderer by shooting out one of its turbine engines through the hull of the boat.