Differences Between the VZ-58 and the AK

First, I'd like to wish all the readers of this blog a very happy 2015.

Quick, identify the firearm in the image below:

Click on the image to enlarge. Public domain image.

If you said something along the lines of "AK-47" or "AKM", then you're wrong. What you're looking at is the Czechoslovakian vz. 58 rifle. The vz. 58 does resemble an AK-47 or an AKM externally, but there are a lot of differences underneath the hood. We will study more about this rifle in this post.

The name "vz. 58" is actually a contraction of "vzor 58' (i,e. "model 58"). The official full name of this weapon is "7,62 mm samopal vzor 58" (i.e. 7.62 mm. automatic firearm model 58"). The number 58 is because this weapon entered service in the year 1958 (the AK-47 is named similarly -- it first entered service in 1947).

After World War II, the Soviet Union started using the 7.62x39 mm. cartridge for its AK-47 and AKM rifles and insisted that all the Warsaw Pact countries use the same cartridge for standardization. Many of the Warsaw pact countries (Poland, Hungary, Romania etc.) adopted the cartridge as well as the AK rifle for their military forces, but the Czechoslovakians decided to only adopt the cartridge, but use their own rifle technologies. They already had a history of developing firearms for 300 years or so, and the city of Brno was most recently known for developing the precursor to the famous Bren gun of World War II. A designer named Jiri Cermak was assigned to develop the new rifle in Brno in 1956 and the new rifle entered service in 1958.

The new rifle was chambered to use the 7.62x39 mm. cartridge, the same as the AK-47. This is about where the similarity between the two ends. What are some of the major differences?

• Action: The AK-47 (and AKM and the rest of the AK family) uses the long stroke piston system, whereas the vz. 58 uses the short stroke piston system. In the short-stroke system, the piston moves for a very short distance (in the case of a vz. 58, it moves 19 mm. (or about 0.74 inches)), whereupon it is stopped by a projection. The short backward movement of the piston imparts a sharp blow to the bolt-carrier, which separates from the piston and then continues backwards due to momentum. In a long stroke system, the piston and the bolt carrier move backward together. This means that the short stroke piston system has a smaller mass of moving parts, since the bolt-carrier weighs less than the combined bolt-carrier and piston together. Therefore, there is less vibration and balance shift due to the moving parts and the vz. 58 is easier to keep pointed to the target.
• Firing mechanism: The AK-47 uses a traditional rotating hammer mechanism, whereas the vz. 58 is striker fired.
• Safety/Fire selector lever: The easiest way to tell if a rifle is a vz.58 or an AK is by looking at the fire-selector lever. The AK-47 family is famous for its clunky large fire selector lever, which is located on the right side of the weapon above the trigger and is cumbersome to operate. The user needs to take the firing hand off the pistol grip to manipulate an AK fire selector lever. The vz. 58 has a smaller, much more ergonomic selector mechanism and the lever can be manipulated without taking the hand off the pistol grip. The following two pictures show the differences (click on the images to enlarge -- the fire selector levers are enclosed in red ovals in the images below):

AKM fire selector lever. Note the length of the fire selector lever and its position relative to the pistol grip.
Click on the image to enlarge.

vz.58 fire selector lever. Notice how it is positioned close to the pistol grip and can be easily manipulated.
Click on the image to enlarge

• Magazine: The AK-47, AKM and vz. 58 all come with 30 round box magazines, however, the vz. 58 magazine is shaped a bit  differently, so it cannot be inserted into an AK and vice-versa. The vz. 58 magazine is also made of a lightweight aluminum alloy and therefore, it is lighter than the steel magazines of the AK family. The vz. 58 magazine can also be loaded via stripper clips, without removing the magazine from the rifle.
• Receiver: The early AK-47 receivers were made of milled steel, until the Soviets mastered the art of producing stamped steel parts from the Germans and the AKM (and all subsequent AK models) all have stamped steel parts. This was done to improve the production rate. The vz. 58 still uses a milled steel receiver. While it takes longer to make a milled steel receiver, it is more rigid and therefore has a bit more accuracy.
• Lock action: The vz. 58 has a tilting lock action with a falling breechblock (similar to Beretta 92)
• Bolt hold-open feature: When the last round has been fired in a vz. 58, the bolt catch locks the bolt carrier to the rear of the gun and it stays open, which alerts the user that the firearm is empty. In an AK, the majority of the magazines allow the bolt to go forward on an empty magazine, therefore, the user cannot easily tell that the rifle is empty.
• Stock: The early vz. 58s were made using beech wood stocks, but they soon switched to using a wood-impregnated plastic stock. If you click on the image of the rifle above to enlarge it, you'll notice that the stock has a somewhat grainy look to it. These stocks are affectionately known as "beaver barf" to collectors and are light, durable and economical. AK rifles use laminated wood stocks (earlier models used normal wood and later models use plastic), which are also durable and cheap to produce, but they are a bit heavier. Later stocks on vz. 58 were made of steel and alloys and designed to be foldable or collapsible. One more difference is that the stock on a vz. 58 is designed to be modular and easily detachable/interchangeable.
• Dust Cover: The receiver on a vz. 58 has no ejection port dust cover, because the receiver is completely enclosed by the bolt carrier. Therefore, the ejection port is huge compared to an AK. This can be easily seen when the rifle is being operated. 
• Disassembly: The vz. 58 is held by two pins and is designed to be disassembled without using any tools.

Even though the AK family and the vz. 58 look very similar externally, the vz. 58 cannot exchange parts with the AK family because of the vast differences in the mechanisms.

The following video makes the differences between the two very clear.

The vz.58 was manufactured between 1958 and 1984 and around one million rifles were manufactured, which means they are not as widespread as the AK family. They still remain in use with Czech and Slovak military forces, and they were exported to some other countries as well (Cuba, Vietnam, India, Indonesia, Ethiopia, Uganda etc.)

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.

History and Development of the Assault Rifle - III

In this post, we will look at the history of one of the most famous assault rifles in history, the AK-47. The AK family is pretty widespread around the world these days, but there are widespread myths about its origins. The Soviet propaganda machine liked to portray that it was an original design entirely invented by a self-taught Russian peasant named Mikhail Kalashnikov. The real truth is actually somewhat different. We will study the history of this firearm in the following series of posts.

In the last post, we saw how the concept of the assault rifle was successfully used by the Germans. Their assault rifle was used against the Soviet Union with great success. The Soviets, in turn, analyzed some captured weapons and decided that it was a pretty good idea. Another major influence was the American M1 Garand rifle, which was also supplied to the Soviets in large quantities by the US and the Soviets decided that they must also have a reliable weapon that fires intermediate power cartridges. They quickly established a factory to manufacture 7.62x41 mm. ammunition, but needed a rifle to go with it. The initial requests for new rifle designs were sent to various Soviet bureaus in late 1943 and by the spring of 1944, at least ten designs were submitted by different groups. The Soviets adopted a design by one Mr. Sudayev and his design was called the AS-44. A limited run of the AS-44 was produced just after WW-II ended and the troops were generally happy with these weapons as they were better than what they had previously. However, the AS-44 was just too heavy and thus the Soviets opened another design competition in 1946.

Meanwhile, in a little known battle, called the Battle of Bryansk in 1942, a certain Russian T34 tank commander named Mikhail Kalashnikov was wounded in combat and made it to the hospital on foot, to receive medical treatment. During his recovery period, he vowed that he would make sure that his country would never be defeated again. While he was lying in bed, he overheard some other soldiers complaining about the quality of the Soviet rifles and his own experiences with the standard Soviet infantry rifles of that period also were similar. Hence, he began to design his own firearm, a sub-machine gun. While his sub-machine gun design was rejected because it was over-complex, his talents as a designer were noticed and he was reassigned to the Red Army's Small Arms Research division. Here, he designed a carbine, which was heavily influenced by the American M1 Garand  rifle's piston driven gas-operated system (if the reader looks at an AK, it uses a gas-operated system almost identical to the Garand, except that the AK has the gas tube mounted on top of the barrel whereas it is below the barrel in an M1 Garand.) While this carbine also was not successful, it was the basis of a new assault rifle that was submitted to the Soviet design competition of 1946, the AK-1 (otherwise known as the AK-46). There were 16 other competing designs originally, with the old AS-44 acting as the benchmark standard and after the first round of trials, the AK-46 was chosen along with entries by A.A. Demetyev (the AD-46 rifle) and F. Bulkin (AB-46 rifle). In the second round of trials, the AK-46 was actually rejected because it did not perform as well as its other rivals, but Mikhail Kalashnikov managed to pull enough strings in the selection committee to continue work on his design and submit a new entry for the next round of trials. He went back to the drawing board with his assistant, Alexandr Zaitsyev, and decided to incorporate design features from other weapons (including some from his competitors, the AB-46 and AD-46!). The design of the AK-46's gas operated systems was already heavily influenced by the M1 Garand and the idea of the long stroke piston attached to the bolt carrier and return spring design were lifted from the AB-46 and the idea of large clearances came from the AS-44 and the safety lever mechanism was from the John Browning designed Remington 8 etc.  The new design was dubbed the AK-47.

The other two designers were also given an opportunity to make design improvements for the next set of trials held in 1947. In the next round of trials, the F. Bulkin design (AB-47/TKB-415) was actually the most accurate of the three weapons and the AK-47 was last.  However, the AB-47 had issues with parts wearing out quickly and the AK-47 beat out the other two handily in tests for durability and reliability. The selection committee made the decision that it is better to have a not-so-accurate-but-durable-and-reliable firearm than wait for an indefinite period for an accurate-and-reliable weapon and hence the AK-47 was chosen over its two competitors. The first version of this was deployed to limited troops between 1947 and 1948.

Initially the design called for a stamped steel receiver pinned at the front, for quicker manufacturing time. However, Soviet machine technology was not advanced enough to do this reliably and there were a large number of rejected receivers. Hence, the decision was made to manufacture the receivers using various machining operations. This made the manufacturing processes slower, but at least they could make reliable receivers this way. Therefore the AK-47 Mark I featured a machined receiver.

Meanwhile, a designer named German A. Korobov began to make an improved assault rifle design himself. Korobov had actually submitted a bullpup assault rifle design (the TKB-408) for the original design competion of 1946, but it was rejected after the first round of testing. Nevertheless, he continued to experiment with other bullpup and traditional rifle designs. By 1952, he switched to using the lever-delayed blowback action invented by Hungarian designer, Paul Kiraly. This led to more accuracy and simpler production for his design. In 1955, the Soviets started another design competition and the improved Korobov design (TKB-517) was submitted to the competition.

Meanwhile, the AK guys were not sitting idle either. They recruited several captured German engineers, including the renowned Hugo Schmeisser (the designer of the StG44) and learned mass production techniques from them. Their new design submission for the 1955 competition was the AKM (AK Modernizirovanniy, the Russian word for "Modernized").

Believe it or not, the TKB-517 pretty much beat the AKM on almost all counts. It was more accurate (especially in full automatic mode), significantly lighter and about 1/3rd cheaper to manufacture. So why did the Soviets adopt the AKM then? Because the selection committee decided that since the troops were already familiar with the AK-47, it would not be a good idea to replace it with a firearm that uses an entirely new design. Hence, the less-reliable, but more familiar AKM beat out the more accurate, but new design, TKB-517.

In the next post, we will look at further developments of the AK-47.

What is the difference between a rifle, SLR, submachine gun, carbine etc.?

A very common question among newbies to firearms history is "What is the difference between a rifle, a sub machine gun, a machine gun, a carbine, SLR, assault rifle etc." This post attempts to point out the differences and name famous weapons of each type.

Rifle: The name "rifle" originally comes from the fact that the barrel of such weapons is "rifled". This means that the barrel has grooves in it to impart spin to the bullet as it comes out of the barrel. This spin helps to stabilize the bullet as it travels through the air and gives it a predictable drift (e.g.) a particular rifle may fire bullets that travel 1-2 cm. to the right every 100 meters on a windless day. This feature allows the user to reasonably predict where a bullet will hit and gives the rifle its accuracy. Earlier firearms, such as muskets, had smooth barrels. Smooth bore weapons were much easier to manufacture than rifles, but lacked in accuracy, as the bullets didn't have stability in the air and deviated in a random direction from the intended target. Therefore, the standard strategy for European armies of that period was to line up men in parallel lines and tell them to all simultaneously open fire at the enemy, because almost no one could reliably hit the enemy that he was actually aiming for. This massed fire strategy worked because some enemy would be hit, even if they weren't the ones that were originally targeted. These days, most modern firearms, even small ones, such as revolvers and pistols, have rifled barrels. Therefore, in modern times, the word "rifle" by itself, implies a firearm that has a rifled barrel, is designed to be fired from the shoulder, is manually fed (i.e. after each shot fired, the user has to manually operate a lever to feed a new cartridge into the weapon) and carries a small number of cartridges internally (say 1 to 5 cartridges). Examples of modern rifles from the early 20th century would be the famous American .30-06 M1903 rifle, the British 0.303 Lee-Enfield, the Mauser M98 etc.

Assault Rifle: In the early part of the 20th century, it was realized by some military forces that most conscripted troops, who were hastily trained in wartime conditions, had less than a 50% chance of hitting a target beyond 300 meters. It was also realized that most infantry encounters occurred at less than 500 meters and rate of firepower was also an important factor in these encounters. It was therefore reasoned that there was no need to give such soldiers a weapon and ammunition capable of hitting targets at 2000+ meter ranges, since most soldiers could not hope to hit a target that far away in the first place. Instead, it was reasoned that it was better to give troops lesser powered (and therefore, smaller and lighter) ammunition to suit the actual ranges that most infantry engagements occurred at and a correspondingly lighter weapon suited to fire this ammunition. With lighter ammunition and weapon, the soldier could carry more ammunition and therefore use a weapon with a higher rate of fire. While the concept was around before World War II, it was the German StG 44 (Sturmgewehr 44) that really popularized the concept. The word Sturmgewehr was coined by Adolf Hitler and literally translates to "Storm Rifle" (the word "storm" being used in the context of "storming a castle" or "assaulting a castle") and the term "assault rifle" is actually a translation of "Sturmgewehr". Even though there were earlier weapons that could be classified as assault rifles, many historians consider the StG 44 as the first to form the concept of modern assault rifles. In these times, an assault rifle is a weapon with the following characteristics:

• Has a rifled barrel (as in the case of the rifle described in the previous section).
• Has provision to be fired from the shoulder, just like a rifle.
• Uses an intermediate powered cartridge. This means that the cartridges are smaller than those used by a regular rifle, but larger than the cartridges used by a pistol. This is one of the key differences between an assault rifle and a regular rifle.
• Is capable of selective fire modes. This means it allows the user to select between firing different numbers of shots each time the trigger is pulled. In semi automatic mode, the weapon will shoot one bullet each time the trigger is pulled. The weapon automatically chambers the next cartridge to fire, but the user needs to let go of the trigger and pull it again to shoot it. In burst mode, the weapon will fire a preset number of cartridges (say 2 or 3) with each trigger pull. In fully automatic mode, the weapon will continue to keep firing as long as the trigger is pulled and there is ammunition. The ability to switch between various modes of fire is a key feature that distinguishes an assault rifle from other types.
• Has a detachable magazine. Most modern assault rifle magazines carry 20 to 30 cartridges or so.

Examples of assault rifles include the AK-47 family, the M16 family etc.

SLR: This is an acronym for "Self Loading Rifle". The term "SLR" is usually used in commonwealth countries. This has some common features with the assault rifle described above. Like the assault rifle, this is also a weapon that has a rifled barrel and is designed to be fired from the shoulder. It also uses an intermediate powered cartridge and has a detachable magazine like the assault rifle concept. The one key difference between assault rifles and SLRs is that SLRs have only one firing mode, the "semi-automatic mode". This means that each time the user pulls the trigger, the weapon will fire only one cartridge. It will automatically eject the fired cartridge, load the next cartridge and prepare the weapon to fire, but the user has to let go of the trigger and then pull it again to fire the next cartridge. This is unlike an assault rifle, which has multiple firing modes and allows the user to switch between them. Examples of SLRs would be weapons like the American AR-15 and the Indian Ishapore 1A1 SLR. The AR-15 is a semi-automatic version of the M16 rifle and the 1A1 is a semi-automatic version of the Belgian FN FAL assault rifle.

Carbine: This is a term used for weapons that are versions of rifles or assault rifles, but with a shorter barrel and lighter weight. Carbines are bigger than pistols, but smaller versions of rifles. In the days of the Wild West, mounted riders preferred a shorter and lighter firearm because these were easier to operate than full sized firearms, when riding. In more modern times, people inside moving vehicles or in close quarter jungle combat, preferred shorter weapons for the same reason. Since carbines have shorter barrels, they lack in accuracy compared to full sized rifles or assault rifles. While they use the same cartridge as their full sized cousins, the shorter barrel also means reduced velocity bullets. Many assault rifles also come in a carbine version. For example, the American M4 (a carbine version of the M16 assault rifle), the Israeli Galil SAR (a carbine version of the Galil assault rifle), Steyr AUG carbine ( based on Steyr AUG assault rifle. The carbine form uses a 16 inch barrel, whereas the assault rifle uses a 20 inch barrel) etc.

Submachine Gun: This is a weapon that shares some similarities with assault rifles, but one key difference is that submachine guns are designed to fire pistol cartridges instead of intermediate cartridges. As a result of this, submachine guns are generally lighter and smaller than assault rifles and are about the same dimensions or smaller than carbines. Since they use pistol ammunition, they also have less recoil and therefore can be fired from either the shoulder, the hip, or even holding it like a pistol. The first weapon to use the term "submachine gun" was the famous Tommy Gun that we studied about earlier. This is a fully automatic weapon that fires .45 ACP cartridges, the same cartridge used by the Colt M1911 pistol. Another famous submachine gun from the World War II era is the British Sten gun, which is also a fully automatic weapon. Modern submachine guns such as the Heckler and Koch MP-5 are capable of selecting multiple firing modes. Submachine guns are more preferred for close-range combat in urban environments because, with lower powered pistol cartridges, there is less risk of bullets penetrating through walls and hitting innocents on the other side

Machine Gun: This generally denotes a weapon that is capable of rapid, fully automatic fire and carries a large supply of ammunition. Fully automatic fire means that the weapon will keep firing as long as the trigger is pulled and there is a supply of ammunition available to it. Most machine guns fire either full sized or intermediate sized ammunition, similar to rifles and assault rifles. Machine guns generally carry a large supply of ammunition in ammunition belts, drum magazines or box magazines. This means that they generally have hundreds of cartridges available to them, unlike the 20-30 cartridge magazines used by assault rifles. They are also generally heavier than rifles and assault rifles. Examples of machine guns would be the Gatling Gun, the Gardner Gun, the Bira gun etc. Modern machine guns include the Browning Automatic Rifle (BAR), the British Bren gun, the American Stoner 63, the Belgian FN Minimi etc.

Shooting: Compensators and Muzzle Brakes

When shooting a firearm, one may notice that there is a tendency for the muzzle to rise up in the air after the shot is fired. This effect is called muzzle climb or muzzle rise. The cause of this is basic physics. Look at the two images below:

When a firearm is discharged, there are multiple forces acting upon it. The gases generated by the burning propellant of the cartridge, pushes the bullet out the barrel and also pushes back on the firearm. This force acts on the centerline axis of the barrel. Let this force be represented by A in the two diagrams above. Now, the user of the firearm is also resisting the kick, by holding the firearm with his hands. Let these forces be represented by B in the diagrams above. Note that for the assault rifle, there are two points where force B acts upon (i.e.) at the stock and at the grip. Also note that in both diagrams, force A is acting at a higher point than force B. This causes the rotational torque C, which causes the front of the firearm to rise.

This effect is more visible for heavier caliber weapons or when multiple shots are fired rapidly. There must be some way to prevent this muzzle climb for happening, because no one wants their weapon to act as though it is on anti-aircraft duty, when they're trying to shoot at a target on the ground!

One way to reduce this effect is if A and B are in the same axis (or fairly close to the same height), then the torque C is minimized. Another way to reduce this is to use devices such as a compensator or a muzzle brake.

Public domain image. Click on image to enlarge

In the above picture, we observe that the gentleman in the front of the picture is firing an AKM assault rifle. Notice that the tip of the barrel has a slanted tip and is slightly tilted to the right as well (it is more visible in the enlarged image). This slanted tip is not due to wear and tear or poor maintenance of the weapon -- it is actually a feature. That device is called a slant compensator. What it does is direct some of the escaping gases upwards, thereby pushing the muzzle down. This counteracts the torque trying to push the muzzle up and thereby makes it easier to keep the weapon pointed at the target. The AKM also has a tendency to move to the right, which is why the compensator is also slightly tilted that way, so that it pushes the muzzle to the left to counteract that movement as well. When the Russians decided to make an improved AK-47 version (the AKM), this was one of the standard features added to the AKM model. This simple device could also be retrofitted to older AK-47 models, simply by screwing on this device to the tip of the barrel.

Another device that is similar is called a muzzle brake. Basically, this consists of a small tube that has a number of perforations along its sides, which is attached to the end of the muzzle. These perforations allow the gases to escape at an angle to the muzzle, which not only helps reduce the muzzle climb, but also reduces the recoil felt at the back of the weapon.

Muzzle brake at the tip of an M16 assault rifle.

Yet another way to reduce recoil is called porting. Basically, this involves drilling precise holes near the end of the barrel, which allows some of the gases behind the bullet to escape upwards as the bullet is exiting the barrel, thereby pushing the barrel down.

Public domain image. Springfield Armory XD-40 pistol with ported barrel.

The advantage of such devices is that they reduce muzzle climb as well as felt recoil. This improves the accuracy of the user. It also reduces the load felt by the user during long shooting sessions.

There are also a few disadvantages of such devices. One is that the noise level of the weapon increases by a few decibels. They also increase the flash seen at the end of the barrel. Some muzzle brakes redirect some of the gases towards the user to reduce recoil, but this could cause some of the pressure wave to be redirected to the user as well as extra noise and flash, thereby causing some discomfort. Additionally, if the shooter is firing from a prone position, the redirected gases could throw up some extra dust towards the shooter, which could impair visibility and give away the user's position. Finally, the extra weight at the tip could affect the overall balance and handling of the weapon.

Sights: Iron Sights: Open Type Sights

In our previous post, we studied some basics about iron sights. Now we will study one of the types of iron sights, the Open sight.

In an open type sight, the rear sight is merely a piece with a notch cut in the middle. The notch is typically V-shaped, square shaped or U-shaped. The front sight is usually some kind of ramp or post.

The above picture is an example of an open-type sight. It is typically made of steel or polymer. Note the rear sight is merely a small piece with a square notch in the center. The front sight is a small post type. In the above example, the front sight is fixed to the barrel, but the rear sight may be slid left or right using proper tools, to adjust the horizontal alignment of the sight. In the above example, the rear sight also has a white line surrounding the notch, to give it greater contrast from the surroundings, to make it easier to aim.

In some cases, the front and rear sights also have small dots of some material that glows in the dark (e.g.) glass tubes filled with tritium gas. This helps in picking up the sights in the dark as well.

Since tritium is a radioactive form of hydrogen, it slowly decays and emits light as it does so. Therefore, sights like these don't need any batteries and could easily last 10 years or more. These sights are much more visible in low light conditions.

These sights are characterized by their simplicity of design. There is not much that can go wrong with them. They are also small and unobtrusive, so they don't affect the balance of the pistol much at all. They also can't get caught easily on clothing or holsters because of their small size and shape. Hard blows may bend or move the sights out of alignment though, but on the whole they are pretty durable. Rain, fog and snow don't affect these sights much at all. These sights are cheap to manufacture and don't use batteries or electronics, so there is less to go wrong.

These sights are not as precise as other sights though. Square shaped notch on the rear sight provides the best accuracy of different open iron sight types. Other types are not as precise and also take longer to aim. Peering through the sights also obscures other details which are covered up by the sides of the sights.

Sights like these are pretty useful up to about 300 meters or so, though most average shooters can shoot them typically to 100 meters or so. These are therefore typically used by shorter range weapons such as civilian shotguns, police revolvers and pistols etc.

One famous assault rifle that was originally designed with open type sights is the AK-47. The rear sight is an adjustable one with a simple V-shaped notch cut on it, while the front sight is a post. The rear sight may be slid forwards and backwards to adjust for range. One may now purchase AK clones with other types of sights as well, but the original version was designed with open-type sights, which is typical for this simple, reliable weapon.

Actions: Gas Operated: Long Stroke Piston

In our last post, we studied the gas operated, short stroke piston action. During this post, we will study the other gas operated action that uses pistons, the long stroke piston. This is a mechanism that was used by the American M1 Garand rifle (not the carbine, which uses a short stroke piston), the Soviet AK-47 family (and its various derivatives made in other countries, such as the Israeli Galil, Finnish Valmet etc.), the Belgian FN FAL assault rifle etc.

Like the short stroke piston we've already studied, when the cartridge is fired, hot high pressure gases are generated which push the bullet out of the barrel. Most of these hot gases also escape behind the bullet, but some of it is tapped out and used to operate the extraction and reloading mechanism to eject the spent cartridge and load the next cartridge.

Click to enlarge image

Original file licensed under GNU Free Documentation License version 1.2 by user Thuringius, on en.wikipedia.org

In the above image, (1) is the gas port from which a portion of the hot gases leaving the barrel are tapped. (2) is the head of the piston and (3) is the piston rod. (4) is the bolt that holds the cartridge in place in the breech and (5) is the bolt carrier that moves the bolt. (6) is the return spring.

Initially, the bolt holds the cartridge in place in the breech chamber. When the trigger is pulled, it releases the hammer (not shown in the image above), which strikes the base of the firing pin (not shown in the image above). The other end of the firing pin strikes the base of the cartridge, which detonates its primer. The primer in turn, causes the propellant of the cartridge to burn and generate hot, high pressure gases. The generated gases expand and push the bullet out of the barrel.

Click to enlarge image

Original file licensed under GNU Free Documentation License version 1.2 by user Thuringius, on en.wikipedia.org

As the bullet is pushed out of the barrel, some of the high pressure gases generated by the exploding cartridge are tapped via the port (1) and enter the tube containing the piston. The high pressure gases act upon the piston head (2) and push it backwards. Since the piston rod (3) is connected to bolt carrier (5), they move backwards, compressing the return spring (6). At the same time, the bolt carrier (5) also picks up bolt (4) and moves it backward at the same time. The bolt has an extraction pin that picks up the spent cartridge case and pulls it out of the breech. As the spent cartridge moves backwards, it is ejected out of the gun via a side port. The piston, bolt carrier and bolt continue to move backwards and re-cock the gun. Meanwhile the high pressure gases acting on the piston head (2) are dissipated via a vent hole in the tube. When the bolt carrier moves backwards to its maximum, the compressed return spring (6) pushes it forwards again. This moves the piston, bolt and bolt carrier forward again and on the way forward, they pick up a new cartridge from the magazine and push it into the breech chamber. Now the weapon is ready to fire again.

In the above animation, you can observe clearly how the mechanism works (including the hammer and firing pin, which were not present in the images above).

The main difference between the long stroke piston action and the short stroke piston action is that in a short stroke action, the piston moves back violently only a short distance (usually less than its own diameter) and then it is stopped by a projection. The bolt carrier then separates from the piston and continues to move backwards due to momentum. As a result of this, a short stroke piston action generally taps gases from closer to the breech (closed end of the barrel). In a long stroke action, the piston moves a distance greater than the length of the cartridge. In fact, the piston stays attached to the bolt carrier throughout the operation. This causes the piston to have greater dwell time and therefore, long stroke piston weapons generally tap their gases closer to the front end of the barrel (the muzzle). It also means that the operating parts are longer and therefore heavier than that of a short stroke piston action.

The advantages of this type of action are many. Like the short stroke piston action, the hot, high pressure gases only act upon the piston head and therefore, the other operating parts (the bolt, bolt carrier, trigger assembly, hammer, firing pin, return spring etc.) are not exposed to the hot gases or the dirty residue at all. These weapons can therefore accept a wide variety of cartridges using different quality propellants, since the dirty residue from low-quality propellants does not have a chance to contact most of the key operating parts of this action. This means a more reliable action and ease of maintenance of the weapon. The extra weight of the piston rod acting on the bolt carrier means more positive extraction, chambering and locking of the cartridges.

There are also some disadvantages. The main one is that the mass of the moving parts alter the center of gravity of the weapon and thereby make it harder to keep the weapon pointed on target, especially when firing in automatic mode. The abrupt stops and starts of the bolt carrier, piston and bolt at either end of the cycle also contribute to the shaking. Also, because the operating parts are longer, the overall weight of weapons that use this action are a bit heavier than short stroke piston actions.

Actions: Blowback Action: Lever Delayed Blowback

In our last couple of posts, we've studied the basic principles of a blowback action and the reason why we want to delay the blowback action. In our last post, we saw that mechanical means can be used to delay the movement of the bolt, by putting it at a mechanical disadvantage by using a couple of rollers (i.e.) the roller delayed blowback action. Another way to achieve the same effect is called a lever-delayed blowback action, which we will study in this post.

When we think of the words "mechanical advantage", the first object that many of us think about is the simple lever. We use a straight rod as a lever, balance it about a fixed pivot (fulcrum) and place the heavy object under the short-end of the lever. We then pull on the long end of the lever. Since we're pulling on the long end, we don't have to apply as much force, but we have to move the lever through a longer distance to move the object a short distance.

Conversely, if we put the object on the long end of the lever and push down down the short end, we put ourselves at a mechanical disadvantage and need to apply a lot more force to move an object. However, pushing down a small distance on the short end will move the object a lot more on the long end.

This is the principle of the lever-delayed blowback action.

Click on image to enlarge and view the animation in all its glory. 

The original image disappeared from the web around May 2013. Luckily I was able to restore it from backup.

In the above image, we have a pretty good animation of how the lever-delayed action works. When the cartridge is fired, the rear movement of the spent cartridge case (the yellow part) acts upon the blue bolt. Before the bolt can move much though, the gray lever rotates and moves the red bolt carrier first, which moves a long way for the short movement of the bolt (the leverage principle we just talked about above). This leverage acting on the bolt carrier increases the force of resistance to movement and slows down the movement of the bolt itself. Once the lever has reached an approximately horizontal position, it ceases to act as a lever and the bolt and the bolt carrier move backwards together at the same speed and are followed by the empty fired cartridge case as well. This extra initial delay in the movement of the bolt serves to keep the gas seal fairly tight until the bullet has left the front end of the barrel and most of the high pressure gases have also gone out the front.

The picture above shows the drawing of an actual weapon (a French FAMAS assault rifle) that uses the lever delayed blowback action. Initially, the cartridge J is in the breech and the hammer H is cocked. When the trigger is pulled, the hammer H releases and strikes the back of the bolt A and the long firing pin E, which strikes the base of the cartridge J, igniting its primer and burning its propellant material. As the bullet begins to leave the front of the barrel, the empty cartridge case J now pushes back on the bolt A, which in turn transmits the force to lever B. The lever B rotates about the pivot C and moves the bolt carrier D faster than the bolt A. Due to this leverage being applied to weight of D, extra force must be applied to A initially to move it. As long as B is rotating, bolt A moves backwards a lot slower than D and therefore the breech stays practically shut. Once B has reached a horizontal position, it ceases to act as a lever and then both A and D move backwards at the same rapid speed, opening the breech. The case J also follows A backwards and is ejected out of a side port due to a spring inside the magazine that is pushing new cartridges upwards. The backward movement of A also compresses a recoil spring in the tube G and also cocks hammer H on the way back. The sear spring mechanism F holds down the hammer H after it is cocked and while the bolt is moving backwards. The bolt moves backwards, continuing to compress the spring G, until it is slowed down to a stop by G and the additional lever and spring K at the back of the weapon. These two then push the bolt forward whereupon it picks up the new cartridge from the magazine and moves it forward into the chamber.

Since this action uses the principle of leverage between A and D, the weights of A and D can be relatively light, since the leverage is what provides the resistance to backward movement of the bolt. This means the weapon can be much lighter than one that is using a straight blowback action. Conversely, the weight savings gained from the lighter action can be re-used to make a heavier barrel and chamber and therefore it can fire a much more powerful cartridge than a straight blowback weapon.

The first lever-delayed blowback action was invented by the famous Danish born US firearms designer, John Pedersen. However, it was perfected by the noted Hungarian firearms designer Paul Kiraly in the 1930s. This action is not used in many weapons, but the most famous current user of this action is the French FAMAS assault rifle.

French FAMAS F1 assault rifle

The FAMAS itself was heavily influenced by the mechanism of the French AA-52 LMG, which was developed after the 1950s and also uses a lever delayed blowback action. The FAMAS is significantly lighter than most assault rifle weapons of its class. Other users of this action include the Dominican Republic San Cristobal 0.30 carbine (designed by Paul Kiraly after he fled Hungary during the communist revolution and settled in the Dominican republic) Brazilian BSM/9 M1 submachine gun, the Italian Benelli B76 pistol and a series of Russian firearms designed by Anatoly Baryshev (AB-7.62, AVB-7.62, LCZ B20).

As an interesting side note, there was also a Soviet assault rifle called the TKB-517 that was developed in the 1950s by a Russian firearms designer named German A. Korobov. Mr. Korobov initially experimented with various assault rifle designs using gas delayed blowback operation throughout the late 1940s. While his earlier attempts were accurate enough, they were not as reliable and therefore, he switched to using a Paul Kiraly designed lever delayed action in 1952, which gave him better accuracy as well as better reliability. In the mid 1950s, the Soviet military decided that they needed to replace the original AK-47 assault rifle with a better design and opened a competition to develop a replacement. The TKB-517 rifle was submitted to the competition against a modified Kalashnikov AK-47 and some other competing designs. The TKB-517 was found to be the most accurate and controllable of all the designs submitted, especially in fully automatic fire mode. It was also much lighter and cheaper to manufacture than even the modified AK, which is quite an achievement in itself. However, the Soviet military decided that the less accurate, more expensive, but familiar and already well established Kalashnikov design was preferable to the more accurate, cheaper, lighter, but newer design TKB-517 and hence, the winner of the competition was declared to be the Kalashnikov designed modified AK, the AKM, which is the most widespread assault rifle in history.

Which has more range, Ak-47 or M-16?

Was recently browsing a forum where this question came up? Which has more range, an AK-47 or an M-16. One poster noted that an AK-47 has 7.62 mm diameter barrel whereas an M-16 uses 5.56 mm. diameter barrel and therefore concluded that higher caliber rounds (meaning, the AK-47) has better range. Another forum poster opined that a TV show he watches has repeatedly mentioned that the M16 bullet has lesser punch than an AK-47, but has greater range and accuracy. So which of these is really true, the reader asks? Let us examine the facts scientifically.

First, bullet caliber has very little to do with range, otherwise civil war era bullets would have much longer range than either of the two rifles. So what does really matter for bullet range? There are a number of factors, such as:

1. Weight of the bullet (which affects momentum and how fast a bullet travels)
2. Amount of propellant in the cartridge.
3. Quality of propellant in the cartridge. Smokeless powders provide more thrust than the equivalent amount of black powder, for instance.
4. Shape of the bullet (ball, spitzer bullet etc.)
5. Amount of rifling or spin imparted on the bullet (which affects the stability of the bullet in the air) and its aerodynamics.

With that said, let us now compare two cartridges, both of which were designed for use with the M16. The first is the M193 cartridge which came out with the original M16 A1 model and the second is the M855 cartridge that came with the improved M16 A2 model. Both cartridges are of the same length (44.70 mm.) The M16 A2 model has a barrel with more rifling, which means the bullet coming out of it spins a lot more than a bullet coming out of an M16 A1 barrel. The M16A1 barrel has a 1 in 12 twist, whereas a M16A2 has a 1 in 7 rifling twist. Even though the bullets of both cartridges are of the same diameter (5.70 mm.), the length of the bullets differ. The bullet from the M193 cartridge is shorter and it weighs about 3.56 gm. whereas the bullet from the M855 is longer and weighs about 4.0 gm. The overall length of both cartridges is the same though at 44.70 mm.

Now let us compare the performance of these two cartridges from the table below:

         5.56 NATO Ball Ammunition Ballistic Comparison
              based on Aberdeen Proving Ground Data
  velocity (fps)    trajectory (in.)  drop (inches)  drift (inches)*
range   M193   M855       M193  M855      M193   M855     M193    M855
(meters)
 0      3,200  3,100     -2.5   -2.5       0.0    0.0      0.0     0.0
100      2,774  2,751     +2.8   +4.4      -2.2   -2.3      1.3     1.1
200      2,374  2,420     +2.7   +5.8      -9.9  -10.2      5.8     4.9
300      2,012  2,115     -4.9    0.0     -25.1  -25.3     14.2    11.8
400      1,680  1,833    -23.0  -15.0     -50.8  -49.5     27.6    22.4
500      1,373  1,569    -56.2  -42.9     -91.6  -86.7     47.5    38.0
600      1,106  1,323   -113.1  -88.2    -156.1 -141.3     76.4    59.5
700        995  1,106   -206.8 -156.1    -257.3 -220.9    113.5    88.4
800        927  1,010   -339.9 -267.7    -398.0 -339.2    156.1   124.9

                                              * Drift for 10 mph wind.
M193 Ball ammunition fired in M16A1 rifle with 250 meter battle sight zero.
M855 Ball ammunition fired in M16A2 rifle with 300 meter battle sight zero.

First thing we notice from the table above is that the bullet from an M193 cartridge initially comes out flying at a faster velocity than the M855 cartridge (3200 fps vs. 3100 fps), which is to be expected, since it is a lighter bullet, and also because the bullet from the M855 is spinning about its axis a lot faster since the rifling on an M16 A2 is more than on an M16 A1. Therefore, a naive person might conclude that the M193 bullet has greater range since it is travelling faster.

However, this is not the end of the story. Look at the velocities once the bullets have passed 200 meters. Suddenly the M855 bullet is moving faster. What is the cause of this? It is because of the spin on the bullet. The M193 bullet is spinning about its axis less and therefore starts to wobble and lose stability in the air earlier. Hence, it encounters more air turbulence and starts to lose its velocity faster. In fact, by the time the bullets have traveled 200 meters, it has lost so much of its velocity that it is now moving slower than the M855 bullet. The situation only gets worse as it travels 300 meters, 400 meters etc. Suddenly, it looks like the M855 bullet may have greater range.

Also observe the drop columns for the two cartridges. Note that up to a distance of 300 meters, there is little difference in the height that these two bullets drop. However, at 400 meters, the bullet from the M193 has dropped 50.8 inches to the M855's 49.5 inches, which is a difference of over an inch. By 500 meters, the difference is almost 5 inches, by 600 meters, the difference is almost 15 inches and at 700 meters, the difference is over 36 inches! So why does one bullet drop to the ground more than the other? Again, this has to do with the bullet velocity. The M193 bullet takes a longer time to reach 500 meters distance than the M855 bullet, because it is moving slower. That means that the force of gravity has a longer time to act on it. Think about it this way: say that it takes 1 second for the M855 bullet to reach 500 meters and 1.1 seconds for the M193 bullet to reach the same distance, since it is moving slower. Now the same force of gravity is acting on both bullets and pulling them towards the earth at the same rate. However, since gravity has only acted for 1 second on the M855 bullet, whereas it has acted for 1.1 seconds on the M193 bullet, therefore the M193 bullet will be pulled closer to the ground. What this means is that if both bullets are fired from the same initial height, beyond 300 meters or so, the M193 bullet will strike the ground first and therefore have lesser range.

Also note the drift columns on the right of the table. Due to the greater spin of the M855 bullet, it is more stable in the air and tends to drift a lot less than the M193 bullet and therefore has more accuracy.

Now let us get back to the initial question about which has greater range, the AK-47 or the M-16. Now these are rifles of different calibers. Let us say that for the sake of argument, we will assume an M16 A2 which uses the M855 cartridge we examined earlier. We will also assume that the AK-47 uses the M43 cartridge, which is one of the more common cartridges used for this weapon. As we know, the AK-47 has a 7.62 mm. diameter barrel, compared to the M-16's 5.56 mm. diameter barrel, therefore the AK-47's bullet has a larger diameter and is also a heavier bullet. The M43 cartridge is 39 mm. long and has a bullet diameter of 7.92 mm. The bullet also weighs between 8 gm. and 10 gm. depending on type of bullet, which means it is much heavier than the M855 bullet, which tops out at 4 gm. The two bullets also have different amounts and types of propellants, which means the velocities of the respective bullets will be affected by this factor as well.

When the M43 bullet is fired, it carries greater momentum than an M855 bullet. This is because of its greater mass. This means that the M43 bullet packs a bigger punch than an M855 bullet because of more momentum. Remember though that momentum = mass * velocity. Even though the M43 bullet has greater momentum, it actually comes out of the barrel slower than an M855 bullet (710 meters/sec. vs. 940 meters/sec.) This means that it initially appears that the bullet from an M855 will travel further than the M43 bullet. But as we've seen previously, initial velocities don't necessarily tell the whole tale. So let us examine what happens after the bullets from both rifles travel a bit of distance.

Unfortunately, after the bullets have travelled about 300 meters, things begin to actually get worse for the M43 bullet. Due to its aerodynamics, it travels slower than an M855 bullet. This means it will hit the ground sooner than an M855 bullet fired from the same height off the ground, which means lesser range.

Therefore, even though the AK-47 bullet has greater momentum and packs a bigger punch than an M16 A2 bullet, it travels a lot slower and hits the ground at a lesser distance than the M16 A2 bullet. Hence the M16 has a greater range than an AK-47.