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.

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.

Enjoy.

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.

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.

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)
10	2739	2627
11.5	2872	2738
14.5	3064	2907
16	3132	2989
20	3259	3095
24	3315	3158
26	3391	3231

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.

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.

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.