Sunday, May 29, 2011

Suppressors a.k.a Silencers - Part I

A suppressor (or a "silencer") is a device that is screwed on to the barrel of a gun and designed to reduce the amount of noise and flash generated by a weapon. Before we start to study about these devices, it is good to clear up a few myths about them (and these myths are mainly due to Hollywood movies). The biggest myth is that they make a firearm almost noiseless -- you only hear a soft "phut" noise, if all the James Bond movies are to be believed. The second biggest myth is that in the absence of a suppressor, you can improvise with almost any cylindrical object (bottle filled with water, coke can etc.)

The first thing to note is that there are multiple sources of noise possible from a firearm:
  1. Noise of the hammer striking the cartridge.
  2. Noise due to the exploding propellant material and hot gases leaving the barrel.
  3. Noise due to the bullet flying through the air (sonic boom, if the bullet is flying supersonic).
  4. Noise due to ejecting the empty cartridge case and cocking the weapon.
  5. Noise due to bullet striking the target.
Of all these sources, #2 and #3 are the main sources of loud noise from a firearm. Let us consider the noise from #2 (i.e. exploding propellant material). This typically hits about 140-160 dB, which is louder than your average heavy metal concert (trust me on this one, I've attended quite a few of them). No suppressor is going to remove such a loud noise like this completely. At the most, a suppressor drops the sound level to around 130-145 dB, with the quietest ones measuring about 117 dB, which is still in heavy metal concert territory. So, what's the use of such a device if it doesn't remove the sound completely. Well, when hearing protection is added, this makes the loudness level easier to bear. These devices also remove the flash emanating from the barrel and thus make it less likely to disorient shooters. They also change the sound signature of a firearm, so that the sound doesn't exactly sound like a shot. As the old Finnish expression goes, "A silencer does not make a marksman silent, but it makes him invisible".  You can observe how the sound signature changes in the below video, where the person fires a 9 mm. pistol, first with no suppressor and then with a suppressor screwed on:

As you may note, the suppressor doesn't completely remove all the noise, but it does remove a fair amount and also the sound no longer sounds like a gunshot.

There were many inventors of silencing devices towards the end of the 19th century, with one patent granted to J. Borrensen and S. Sigbjornsen for a device that "lessens the sound of discharge" in 1899. However, the earliest successful commercial suppressor was invented in 1908 by the American inventor, Hiram Percy Maxim, the son of Sir Hiram Stevens Maxim, the man who invented the first portable automatic machine gun. His device consists of a hollow cylindrical tube with a number of expansion chambers in it.

This device is screwed on to the end of the barrel. Expanding gases from firing the cartridge are trapped by the baffle plates, while the bullet travels through the hole in the center. The trapped gases expand and cool and thereby exit out of the barrel with less pressure and velocity, which reduces the noise. This device was sold under the trademarked name "Maxim Silencer", which is probably why we still call suppressor devices as "silencers" even though they don't actually silence a firearm completely.

Mr. Hiram P. Maxim also had interests in the emerging automobile industry and he developed a similar device to reduce engine noise, which we still use today: the muffler, which is also known as a "silencer" in some parts of Asia and Europe.

Since these devices don't entirely remove the noise, the firearms industry prefers to call them "suppressors" instead of "silencers". In our next post, we will look into more about such devices.

What is a wildcat cartridge?

A wildcat cartridge is a custom made cartridge, usually made by modifying an existing commercial cartridge, in order to optimize cartridge performance (e.g. more power, more velocity, better accuracy etc.) Since these are custom made, they are more expensive than normal cartridges. Also, wildcat cartridges are usually used mainly by very serious shooters and hand-loading fans, there is only a limited market for them and larger cartridge manufacturers generally don't make them.

In terms of variety, there are more wildcat cartridge varieties than commercial production cartridges. However, many of these varieties are produced in very small quantities indeed.

In some cases though, some cartridges started out as custom-made wildcat cartridges, but gained enough popularity that they began to be commercialized (i.e. rifles chambered for them are now available commercially) and SAAMI standards were specified for them. Examples of such cartridges are the 6.8 mm. SPC, which was originally developed in collaboration with some members of US SOCOM. The 6.8 mm SPC is based on a .30 Remington cartridge, modified to .270 caliber and then further modified in length to fit in an magazine that can be fitted into the magazine wells of the M16 rifle. Therefore, any M16 or AR15 type rifle only needs replacing of the barrel, bolt and magazine to use this new cartridge. This cartridge is more lethal than the standard NATO 5.56x45 mm. cartridge fired by the M16 and while it is not officially adopted by the military, it has found use by special forces troops in Afghanistan and Iraq and is gaining popularity as a commercial civilian round. Another example is the well-known .357 magnum cartridge developed by Smith & Wesson, which was originally developed from a .38 Special cartridge. The .357 and .38 Special cartridge are both the same diameter externally and only differ slightly in length, because of safety reasons. Early versions of .357 magnum were actually identical dimensions to .38 special cartridges and the length was only altered so that people could not accidentally load the more powerful .357 magnum cartridges into a firearm not designed for the additional pressure. Another example is the 6 mm. PPC (Palmisano & Pindel Cartridge, named after its inventors, Lou Palmisano and Ferris Pindell). This cartridge started out as an improvement of the .220 Russian cartridge, which was itself based on the venerable 7.62x39 mm. cartridge used on the AK-47 and AKM assault rifles. The 6 mm. PPC case is made by forming the .220 Russian brass case into a new shape and is specially geared for single-shot bench rest shooting. It is one of the most accurate cartridges available up to 300 yard ranges and has been produced since 1975 and used in several competitions.

As mentioned earlier, wildcat cartridges are generally used by very serious shooters mainly and quite a few require barrel modifications also in order to use the modified cartridge. The modified barrels are usually supplied by custom barrel makers, who typically work out of small shops. The custom barrel makers generally also supply the buyer with reloading tools and dies, so that buyers can make their own cartridges. Some barrel makers also supply data about how different powder brands, powder quantities and bullet weights perform with their barrels. Therefore, most wildcat cartridges are developed, either by the custom barrel makers themselves, or by someone who is working in conjunction with a custom barrel maker.

.243 Winchester Ackley Improved wildcat cartridge on the left, compared to a normal .243 Winchester cartridge on the right.
Note the reduced case taper and sharper shoulder angle in the Ackley Improved version, which leads to more case capacity and therefore, more propellant.
Image copyright Arthurh at wikipedia and licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License. 

There are many reasons why people develop wildcat cartridges, such as:

  • Increasing the case capacity (as in the Ackley Improved cartridge pictured above) allows adding more propellant to the cartridge, which increases the velocity of the bullet and therefore, the energy transferred by the bullet.
  • Reducing the bullet's caliber increases its velocity, thereby increasing its resistance to wind drift.
  • Better consistency can be achieved by tuning a bullet's diameter, weight and velocity to a particular amount and type of propellant, which leads to greater accuracy.
  • Feeding issues of certain types of ammunition can be fixed. For instance, it is not possible to reliably fire hollow-point bullets with .45 ACP pistol ammunition because of feeding issues from the magazine. Hence, the shape of the cylindrical cased .45 ACP cartridge was modified to a bottlenecked .45 cartridge to solve this issue.
  • Some shooters like to use rifle ammunition with pistols, for greater accuracy. In this case, one starts out with a rifle cartridge and then reduces its case capacity so that it can be used with a pistol.
A wildcat manufacturer generally starts out by using a commercial cartridge case and changing its shape to new dimensions. Usually, this involves pushing the shoulder of the cartridge backwards or forwards as needed to modify the case capacity and also changing the diameter and length of the cartridge neck. This process can be done by either cold forming (i.e. the case is pushed into a die and pressure is applied to change the shape of the case) or fire forming (i.e. the case is placed in a chamber of a different dimension and loaded with a light gunpowder charge. Upon firing the charge, the case takes the shape of the new chamber). Sometimes a mixture of both methods is used to make the final case shape of a wildcat cartridge. Next, the manufacturer trims the case to the appropriate length, because cold forming or fire forming generally tends to increase the length of the case's mouth and the excess length needs to be trimmed. Then the diameter of the neck is changed as needed for the new bullet. The cartridge is then hand-loaded carefully and a bullet is crimped on.

In quite a few situations, firearms can be very easily modified to use the new wildcat cartridges. For example, the Ackley Improved cartridge shown above could easily be used by rechambering an existing firearm. Better still, a firearm that is chambered for the "Improved" cartridge can also fire standard factory loaded ammunition as well, which allows the owner to use less expensive and commonly available ammunition if there is a shortage of wildcat cartridges. Ackley Improved family of cartridges were developed by Patrick Otto Ackley, a prolific gunsmith and author, who produced many improved versions of commercial cartridges in several different calibers.

History and Development of the Assault Rifle - X

With the advent of bullpup designs in the 1970s such as the Austrian Steyr AUG and the French FAMAS, some of the newer designs that have emerged since then have largely been bullpup designs. Some of these include the British L85A1 and L85A2 of the 1980s, the Chinese QBZ-95, the German Heckler & Koch G11, Singapore's SAR-21, Israel's Tavor TAR-21 etc.

Since the advent of the 5.56x45 mm. NATO cartridge, the world has essentially gone into three basic calibers as far as militaries are concerned: the NATO 5.56x45 mm. (used by M16, Steyr AUG, FAMAS, L85, INSAS etc.), the Russian 5.45x39 mm. (used by AK74 family) and the Russian 7.62x39 mm. (used by AK-47, AKM and clones such as the Type 56). The first two of these are generally used by most military forces, whereas the third cartridge is generally widespread among many insurgent groups due to the popularity and wide-spread nature of the AK-47 and AKM family of assault rifles. However, there has been some other significant research in cartridge developments as well. Both the UK and the US did some work to find an intermediate cartridge between the NATO 5.56x45 mm. and the older NATO 7.62x51 mm., in order to strike a balance between bullet effectiveness and recoil force. This was due to the 7.62x51 mm. cartridge having too much power and weight and the 5.56x45 mm. not having sufficient range for some applications. Experiments showed that cartridges such as the 6x45 mm., the Grendel 6.5x38 mm. or the Remington SPC 6.8x43 mm. strike a pretty good balance by having more range than a 5.56x45 mm. cartridge, but still having relatively less recoil and less weight than a 7.62x51 mm. cartridge. With combat in Afghanistan taking place over longer ranges and the advent of scopes on assault rifles, it is possible for an infantryman to engage over longer ranges now and hence there have been noises made in various quarters to replace the M16 with a newer rifle using one of these cartridges instead.

Newer bullet designs using exotic technologies were also tried out during the 1970s and 80s, but they've been much less successful in this regard. For instance, there were attempts to design cartridges that fired flechette darts instead of conventional bullets. However, the cost of ammunition was prohibitive and thus this never became popular. Another exotic concept was folded ammunition, which was ammunition that was roughly U-shaped. The idea was to reduce the length of the cartridge in order to speed up the firing cycle of rifles.

Folded ammunition examples. Click on images to enlarge.

Folding ammunition never caught on either. Another concept was the caseless ammunition cartridge, for which a lot of work was done by Hecker & Koch and Dynamit industries. The idea is that since a caseless cartridge doesn't have a brass case, there is no need for the rifle to eject it after every shot, which reduces the number of steps in a firing cycle and thereby enables faster firing rates. H&K developed the G11 assault rifle to use caseless ammunition. The concept of a consumable cartridge is actually a very old one, as it was used by the Dreyse Needle Gun of 1835! However, with automatic weapons and modern ammunition, there are more problems to solve. For one, caseless cartridges are more easily damaged by rough handling since they don't have a hard outer case and two, the brass case removes some of the heat from the chamber of the firearm and the lack of a brass case means that caseless ammunition could cook-off in a hot chamber. H&K solved the first problem by putting cartridges in a sealed plastic case and had to spend a lot of time developing special propellants to solve the second issue. The G11 was about to be adopted by the West German military when the Berlin wall came down and the cold war ended. This resulted in cutbacks in military spending and H&K went into financial difficulties as a result and was acquired by the British, where they earned their keep by helping fix problems with the British L85 assault rifles. Interest in caseless ammunition technology has been renewed since 2004, due to the US military's Lightweight Small Arms Technology (LSAT) program.

Oddly enough, despite most of the new rifles being bullpup layouts, the US military is looking at conventional layouts for their M16 replacements. For instance, the US Army has switched to the M4 (which is the carbine form of the M16). The (now cancelled) XM8 project, which was designed to replace the M16, also had a conventional layout:
XM8 Assault Rifle. Click on image to enlarge. Public domain image.

The FN SCAR, adopted by the US Special Operations Command (SOCOM) as well as the US Marines M27 Infantry Automatic Rifle also use conventional layouts. Thus, it appears that the US is definitely not bucking the bullpup-layout trend, at least in the near future.

Another interesting concept developed in Australia is the Metal Storm rifle, where many bullets are stacked head to tail in series inside a barrel, with propellant between the bullets. Ignition of individual cartridges is accomplished electronically. Since the cartridges are completely consumable and because they are stacked one behind the other in line, there is no need for case ejection or a feed system to load new cartridges in the chamber. This makes the firing rate much faster than other designs, as well as contributing to reduced weight. As of now, Metal Storm products have found limited use and support from the US Marines.

Monday, May 16, 2011

History and Development of the Assault Rifle - IX

A couple of posts ago, we saw how the US adoption of the M-16 and its 5.56x45 mm. cartridge led to the various member countries of NATO also standardizing the same caliber cartridge in their forces. Some NATO members adopted the M-16 as their standard rifle as well, whereas some others designed their own rifles to use the new NATO cartridge. One of those countries was Austria. At that time (late 1960s), the Austrians were using a variant of the FN-FAL, which used the previous NATO standard cartridge of 7.62x51 mm. The Austrian military decided to make an all new rifle design to replace their old rifles.

Design and development duties of the new rifle was handed to the Steyr-Daimler-Puch company, in collaboration with the Austrian military.The Steyr-Daimler-Puch company has a long history in Austria as a manufacturer of vehicles and firearms. In fact, when Steyr was first founded in 1864, its primary business was manufacture of rifles and they only branched out into making bicycles in 1894 and automobiles in 1915. It later merged with the well known Daimler-Puch automobile manufacturer in 1934 to become Steyr-Daimler-Puch. After World War II, the company gained some bad reputation, as it later emerged that its managing director was the first to suggest using concentration camp slave labor in their factories. However, its reputation did not suffer much after the war and it still remained a manufacturer of heavy vehicles, offroad vehicles, bicycles, small mopeds and scooters. In the US, their mopeds and scooters were sold by Sears Roebuck under the Allstate brand in the 1950s and 60s. In India, their Puch Maxi Plus moped model (made in India in collaboration with Hero Motors and sold as the Hero Puch) was in production until 2003!

During the development process of the new rifle, the Austrian military placed the Office of Military Technology under one Colonel Walter Stoll in charge of development from the military side, while three men, Horst Wesp, Karl Wagner and Karl Moser handled things from Steyr-Daimler-Puch's end. The result was the Steyr AUG rifle.

Steyr AUG Assault rifle. Click on image to enlarge.
Image licensed from Steyr Mannlicher GmbH & Co. under the Creative Commons Attribution 2.0 License.

The letters AUG stand for Armee Universal Gewehr (i.e.) Universal Army Rifle. From the beginning, the AUG was designed as a family of firearms (i.e.) a carbine, an assault rifle and a Light Machine Gun (LMG). This means that many parts between these three are interchangeable. It also was one of the first successful bullpup designs. Design of the rifle was completed in 1977 and it was accepted by the Austrian military in the same year as the StG 77 (Sturmgewehr 77). Since then, it has been adopted by various countries around the world.

While many people think that the Steyr AUG was a very revolutionary design when it first came out, a lot of the features on it existed long before the rifle was conceived. For example, the idea of a family of rifles (i.e. carbine, assault rifle and LMG) sharing many parts in common is not new. The same modular concept was already used successfully by the Soviet designer Fedorov during World War I. In fact, we studied about Fedorov's design earlier in our first installment of assault rifle development. Another misconception is that the AUG is the first bullpup design. The truth is that while it was one of the first commercially successful bullpup designs, it was not the first bullpup design and not even the first military bullpup design. The original bullpup rifle was the British Thorneycroft carbine from 1901. Additionally, the French FAMAS (also a bullpup) was also being developed at around the same time as the AUG. The use of plastics in the weapon was also not a new idea, as the Soviet-made TKB-408, which was designed by German Korobov also had plastics, as did the French FAMAS rifle. Finally, the built in telescopic sight was also not a new innovation, as it was already a feature of the British Enfield EM-2 rifle (also a bullpup design) from the 1940s and a Canadian FN FAL variant in the 1950s.

The real technical merit of the AUG is taking a group of very good ideas and combining them all into a successful design.

Tuesday, May 3, 2011

History and Development of the Assault Rifle - VIII

In the last few posts, we saw during the development of the M-16 rifle, that the US military had determined that "small is beautiful" and therefore used smaller-caliber, but higher velocity ammunition for their assault rifles. The chief motivation for smaller ammunition was because studies had shown that the side with the most firepower tended to win infantry engagements. However, this meant that each soldier would need to carry a larger amount of ammunition, so the US decided to research smaller calibers, which are lighter and therefore a soldier can carry more of them. Research showed that 5.56x45 mm. cartridges were lethal enough at ranges where most infantry combat took place and so they developed assault rifles around this concept: the M16 family.

The results of this research did not go unnoticed by the Soviets. At that time, the Soviets were using the AKM assault rifle as the standard rifle for their military. The AKM and its predecessor, the AK-47, fire 7.62x39 mm. cartridges. In line with western findings, the Soviets also decided to develop another assault rifle, one that uses smaller bullets than the AKM or AK-47. Of course, they did not want to copy the same 5.56x45 mm. cartridge as used by the West, because the Soviets went to great pains to ensure that their own weapons could not be used against them. Hence, they designed a new cartridge of size 5.45x39 mm. and designed a new assault rifle that used the same basic mechanism as the AKM, but scaled down to use the new cartridge. Since the new rifle and cartridge were developed in 1974, the new rifle was called the AK-74. This rifle is still in use in the Russian military.

AK-74 assault Rifle. Click on image to enlarge. Public domain image.

The AK-74 is heavily based on the AKM design, so much so that about 50% of the parts (pins, screws, springs etc.) are interchangeable between the two, even though they are of different calibers. However, the AK-74 also has a bunch of other improvements over the AKM, in order to increase reliability, accuracy and durability. For one thing, the bolt extraction claw is larger on the AK-74 to better extract spent cartridges. The stock is lighter on the AK-74 and was originally made of laminated wood, with cuts on the side to save weight. The stock, pistol grip and hand guards were all later changed to a polymer. The magazine is made of a polymer plastic, unlike the metal magazines of the AKM or AK-47. The magazine also has two extra horizontal ribs in it, which make it impossible to insert it into an older AK family rifle.

Other variants of the AK-74 have folding metal stocks (AKS-74 and its carbine variant, AKS-74U)

A variant called the AK-74M does away with all the wood and the stock, pistol grip and hand guards are all black or plum colored plastic.

AK-74M assault rifle. Click on image to enlarge. Public domain image.
Note the lack of wood in the above rifle.

The AK-74M also has a mounting rail on the left to attach other hardware such as telescopes. Since the early 1990s, the AK-74M model is the current official rifle of the Russian military and is gradually replacing the older AK-74 and AKS-74 models in service.

The Russians have also designed the AK-101, AK-102, AK-103, AK-104 and AK-105 assault rifles, but these use the same AK-74 design, but are chambered for different calibers instead. For instance, AK-101 and its carbine form, the AK-102, are chambered for the NATO 5.56x45 mm. cartridges and are specially designed for the export market.

Sunday, May 1, 2011

History and Development of the Assault Rifle - VII

In our last post, we studied how the AR-15 rifle was morphed into the M16 A1 model. Where we last left off was during the Vietnam war.

The original design for the M16 had a number of flaws: lack of cleaning kit, no chrome lining on the inside of the barrel or chamber, issues with cartridges etc. These flaws became more evident during the Vietnam war, but sadly, only after a number of US servicemen lost their lives. Soon after a Congressional investigation, fixes were made for all these issues and the rifle became a much more reliable product. However, the bad reputation earned by its early flaws took a lot longer to clear.

By 1970 though, the M16's reputation was established and other countries also wanted their own M16 style rifles. The NATO member countries decided to standardize on the 5.56x45 mm. cartridge, which was also used by the M16 A1 model, but they wanted to make improvements to the US version of the cartridge, in particular, because of improvements to body armor technology. The US version of the 5.56x45 mm. cartridge was called the M193 and tests had shown that it didn't penetrate newer body armors that well. The British, Germans and Belgians all presented cartridges that all had the same 5.56x45 mm. external dimensions, but had different bullet shapes and materials that offered much better ballistics and penetrating power than the M193. In the end, the Belgian designed SS109 (which has a bullet with a steel tip) was chosen as the NATO standard. The Belgians also designed a tracer round, L110, which had better performance than the old M196 tracer round. The M196 could burn out in 450 meters, whereas the L110 could show its trail to 800 meters. However, it was found that the M16 A1's barrel rifling twist rate of 1/12 inch (i.e. 1 turn every 12 inches or 1 turn every 300 mm.) was not adequate to stabilize the SS109 or L110 bullets past about 90 meters or so. New barrels with a faster twist rate were required to get the best performance out of the SS109. The ideal rate for a bullet from a SS109 cartridge is at least 1 turn in 9 inches (1 turn in 229 mm.), but the L110 requires at least 1 turn in 7 inches (1 turn in 180 mm.) to continue to be stable for much longer ranges (over 800 meters or so). Hence, it was decided to make a new version of the M16, the model A2, which would feature a barrel with a 1 turn in 7 inch twist rate.

It was also found during the Vietnam war, that many soldiers would put their M16s into full-automatic mode and when in a firefight, new soldiers would often hold down the trigger and shoot entire magazines into the bushes in a few seconds, without killing a single enemy. This caused many of them to run out of ammunition prematurely. Also, the act of firing in full-automatic mode makes the rifle more difficult to control and thereby reduces accuracy. The US military conducted various tests a decided to replace the full-automatic firing mode with a three-round burst mode (i.e. upto 3 rounds would fire when the trigger is held down), because the three-round burst was determined to be the optimum balance between accuracy, ammunition conservation and firepower. The US Marines were the first to request the development of the M16A2 model based on the Vietnam war experiences.

M16A2 model. Click on image to enlarge. Public domain image.

Along with the newer barrel with the 1:7 inch twist rate and the three-round burst mode, there were numerous other improvements made to the M16A2. The thickness of the barrel in front of the front sight was made thicker, to avoid bending the barrel in the field and to also resist overheating better, thereby allowing firing the weapon for longer periods of time. The front and rear sights were improved and the rear sight was made adjustable for ranges between 300-800 meters using the SS109 cartridge (which had different ballistics than the M193). The recoil compensator at the end of the barrel was closed at the bottom, so it would not kick up dust when fired in the prone position. A deflector was attached immediately behind the ejection port, so that left handed users would not get hit in the face by a hot ejected case. The grips were improved and the handguards were made symmetrical so that there was no need to manufacture spare parts for left and right side. With advances made in polymers, the buttstock was re-engineered to use a new plastic that is 10 times stronger than the original stock on the M16A1. The buttstock was also made slightly longer than the original version.

The M16A2 model was first adopted by the US Marine Corps in 1982, followed by the US Army in 1986 and then the other branches of the US military, as well as military forces of other countries worldwide. It is still being used by many users and is the most common variant in the M16 family.

The M16A3 model came out around the same time as the M16A2, but was made in very small numbers indeed. The M16A3 is very similar to the M16A2, but retains the original full-automatic firing mode of the M16A1 instead of the three-round burst mode of the M16A2. This variant was made for US Special Forces, who need the extra firepower afforded by the full-automatic firing mode. Special forces personnel are trained to maintain better fire discipline and not use up their ammunition so quickly. The US Navy was the first to order this variant, for use by its SEAL and Seabee units.

The M16A4 and the M4 are the latest variants of the M16 family.
M16A4 rifles. Click on image to enlarge. Public domain image.

The M16A4 is currently being issued to US Marine Corps front line units, and some US Army units. The main difference between this and the M16A2 is the removal of the fixed carrying handle/rear sight, which is seen on the M16A2. Instead, this is replaced by a Picatinny rail on the A4 model. This allows the user to not only attach a carrying handle, but also other accessories, such as a scope, as seen in the image above. The hand guards in front of the magazine are also of a new design (Knight Armament's M5 RAS handguard), which allows the user to attach a vertical grip, tactical light, laser sight etc.

The M4 variant is a carbine firearm and is a shorter and lighter version of the M16A2. It is intended to replace the M16 in most units of the US Army.

The M16 rifle had initial teething issues, but has later evolved into a fine, reliable weapon, which is in use by several military forces around the world.