How do Firing Mechanisms Work - IV

In our last post, we saw a video that showed the basics of a bolt-action firearm, A bolt action is in the class of manually operated firearm actions. In today's post, we will study a few different classes of firearm actions, which we have already studied the basics of many months ago.

1. Manual bolt action.
2. Gas operated action.
3. Blowback action.
4. Recoil action.

In the above links, we studied these actions using some illustrations and also studied some specific variations of these actions (e.g.) short recoil action, long recoil action, direct gas impingment, short stroke gas operation etc. We also studied examples of weapons that used these different actions.

Thanks to the efforts of the US Army, we actually have a movie that illustrates the basics of all of these actions.

The video clearly illustrates how the various actions work, far better than static images do. Happy viewing!

Parts of the Firearm: The Bolt Carrier Group

In our previous post, we studied the parts of the gun that comprise the fire control group (a.k.a. the trigger control group). In this post, we will study another group of components, the bolt carrier group (or BCG).

The bolt carrier group is usually found in firearms that have a gas operated action. These are the parts that control extracting the old cartridge, cocking the firearm and loading a new cartridge. There are several parts that comprise the bolt carrier group:

Disassembled parts of the bolt carrier group from an AR-15 rifle

In the above image, we see the main parts comprising the bolt carrier group of an AR-15 rifle. There are seventeen parts that comprise the bolt carrier group for the AR-15. They are:

1. Bolt (A)
2. Ejector (B)
3. Ejector spring (C)
4. Ejector roll pin (D)
5. Extractor (E)
6. Extractor pin (F)
7. Extractor spring (G)
8. 3 gas rings (H)
9. Bolt carrier (I)
10. Bolt cam pin (J)
11. Bolt carrier key (K)
12. 2 Bolt carrier key screws (L). These attach the bolt carrier key to the bolt carrier.
13. Firing pin (M)
14. Firing pin retainer pin (N)

There are eight basic operations that are done by the bolt group on an AR-15 or M-16:

1. First, the bolt is in its rearmost position. The action spring then pushes the bolt forward and as it moves forward, it picks up a bullet from the magazine and pushes it towards the chamber via the feed ring.
2. As the bolt carrier moves forward, the bolt passes through cuts in the barrel extension and a cam pin causes the bolt to rotate, so that the locking lugs on the bolt are locked as the bolt reaches its forward most point.
3. When the user pulls the trigger, the sear releases the hammer (we covered these parts in our last post about the trigger group). The hammer spring then rotates the hammer with force into the back of the firing pin (which is part of the bolt carrier group). The firing pin passes through a hole in the middle of the bolt carrier and the bolt and the other pointy end of the firing pin strikes the primer of the cartridge, thereby firing the weapon.
4. Fourth, as the bullet leaves the barrel, some of the gases behind it are tapped into a gas tube. The hot gases travel down the tube, down through the bolt carrier key and are redirected forward, pushing the gas rings on the bolt. This pushes the bolt forward slightly and the bolt carrier to the rear. The rearward movement of the bolt carrier pushes against the cam pin that caused the bolt to lock in step 2. This cam pin now causes the bolt to rotate in the opposite direction and unlock the lugs that were locked in step 2. The bolt is now free to move backwards.
5. As the bolt carrier group moves to the rear, the extractor removes the old cartridge case from the firing chamber and pulls it backwards.
6. As the bolt carrier continues to move backwards, it re-cocks the hammer.
7. As the bolt moving backwards goes past the ejection port, an ejection spring forces the now empty cartridge case to be pushed clear of the extractor and out of the ejection port.
8. Once the bolt has reached backwards to its rearmost point, the action spring pushes the bolt forward again, as described in step 1 and the entire cycle repeats.

The following video gives a decent animation of how things work:

As with the fire control group, it is possible to purchase the parts individually or purchase an entire pre-assembled bolt carrier group part which is ready to be dropped into a firearm. There are aftermarket bolt carrier groups that are plated with hard chrome or titanium nitride for better lubrication and reliability. Some are heavier for slower cycling and others are lighter for reduced loads and faster cycling. Still others are built to much more precise tolerances for consistent locking etc. There is a large selection for users to choose from, depending upon needs and preferences.

What is Limp Wristing?

We sometimes hear the term "limp-wrist" in firearms terminology. So what is it? Is it a good thing or a bad thing? What should we do to counter it? This post aims to answer all these questions.

In the various posts in the past, where we dealt with semi-automatic and automatic firearms, we studied several different actions: recoil operated action, gas operated action, blowback action etc. The previous links can serve as a refresher course for the uninitiated reader of the basics of these various mechanisms. The one thing in common is that the firearm uses a force (either from recoil, gas pressure etc.) to push back the bolt or slide of the firearm, which then removes the old cartridge and cocks the weapon on its way back. It also compresses a spring on the way back and this spring pushes the slide or bolt forward, whereupon it readies itself to fire the next round.

Now, imagine what happens if there isn't adequate resistance offered to the firearm's frame during the backward movement of the bolt or slide (i.e.) if the frame of the firearm is allowed to move backwards with the bolt or slide. Then what will happen is that the operating cycle may not properly complete and the old round may not get ejected in time and the next round may get jammed, rendering the firearm temporarily inoperable. There are a few reasons for this phenomenon to occur, but one of the common reasons is because the user had a loose grip on the firearm, which is why it is called as "limp wristing".

Limp wristing isn't confined to pistols alone. For instance, a rifle or shotgun may also have problems operating properly, if the user doesn't provide a firm shoulder to  rest the butt on. Model of firearm also  has a lot to do with it, as some models are more vulnerable to jamming due to limp wristing than others. Also, the  caliber of the firearm and the recoil force that can be withstood by the user all play a part.

Obviously, the major cause is because the frame was not held firmly enough during the backward movement of the firearm action. So, the easiest fix is to maintain a stronger grip, perhaps by using a two-handed stance with a pistol instead of one hand. Some of the good two handed stances we studied previously are: weaver stance, chapman stance, isoceles stance etc. Similarly, for rifles or shotguns, the user may try improving their stance or grip to make sure that the rifle is firmly braced against the shoulder before pulling the trigger.

In some situations though, the user may just be too weak to provide a good grip, or have some kind of physical deformity which causes issues. In this case, a modification will need to be made to either the firearm or the ammunition.

In the realm of firearm modifications, the user may simply pick another firearm of a different caliber or type. For instance, a firearm with a heavy steel frame absorbs the recoil energy better than one made of a polymer type frame and rely less on the user grip strength to operate.

Yet another firearm modification could be to reduce the stiffness of the recoil spring to make the firearm operate properly.

The user also could choose a firearm that uses a different mechanism to operate, which is not vulnerable to limp wristing problems. For example, the user could choose a single-action revolver to use instead of a pistol. Similarly, a rifle with a manually operated action may be picked instead of one that uses a semi-automatic action.

In the realm of ammunition modification, the user may simply use some different ammunition that burns with a different rate which could cause the limp wristing problems to go away.

In the video below, a person demonstrates using a loose grip with different pistols:

The interesting thing to note in the clip above is that not every pistol jams even with a loose grip and even the ones that jam do not necessarily do it every single time. Some, like the Glock 17, seem to be more sensitive to grip strength than others.

Happy viewing.

Actions: Gas Operated: Recap

Let us now recap what we've learned about gas operated systems in the last few posts:

1. Gas operated systems work by utilizing some of the high-pressure gas generated by firing a cartridge, to operate their extraction, reloading and cocking mechanisms.
2. These are generally used for weapons like rifles and shotguns. For example, most modern self-loading and assault rifles designed during and after World War II use gas operation. Examples include: AK-47 and its descendants, FN FAL, M16 family, M1 rifle and carbine, Valmet, Galil etc.
3. The two main ways of using a gas operated system is to (a) make the gas act upon a piston, which drives the rest of the system or (b) make the gas directly impinge upon the bolt and bolt carrier.
4. Main problem with gas operated systems is that the gas tends to leave corrosive deposits on the working parts. Different gas operated systems handle this issue in different ways.
5. Another problem with gas operated systems is that the heat from the gas causes metal parts to expand. Due to unequal expansion rates of the various components, they must be well lubricated to prevent excess wear and tear.
6. Because of the weight of the parts moving after the weapon is fired, gas operated systems using pistons lose some accuracy because of the vibrations and shift in balance. This especially significant in the case of automatic firing weapons. This problem is reduced with direct impingement systems because the mass of moving parts is lesser than a piston driven system.
7. On the other hand, piston driven systems are generally more reliable because the gas only acts on the piston and is not allowed to directly act upon the rest of the mechanism. Direct impingement systems need to be cleaned and maintained more regularly because the gas acts upon much of the mechanism.

As we mentioned above, the hot high pressure gases generated by an exploding cartridge often carry corrosive chemicals with them. Upon cooling, these chemicals deposit upon the operating parts of the action. If the build up is too much, this will lead to jamming and reliability issues. All gas operated systems must therefore have some way to deal with this situation. For example, in piston driven systems, the gas is only allowed to act on a piston, thereby protecting the rest of the parts from heat and corrosion. Additionally, on an AK-47, the piston has sharp edges on its face, which in theory, scrape the built-up deposits from the walls of the cylinder. These scrapings get vented out the next time the weapon fires. In direct impingement systems such as the M-16, some parts such as the gas tube are somewhat self-cleaning and not designed to be user-serviced in the field. Other parts, such as the bolt and carrier are designed for easy access, so that they can be properly cleaned.

Most modern assault rifles and squad automatic weapons (SAW) in use today utilize the gas operated action principle. This shows the popularity and success of this type of mechanism.

Actions: Gas Operated: Gas Trap

In this post, we will study a lesser known gas-operated system known as the Gas Trap system. This was only used for a few rifles in history, but it might be well to mention it now. This system was originally invented in 1909 by Danish firearm designer, Soren Bang, and used in what is known as the Bang M1922 rifle. The Bang rifle was used by both Denmark and the United States.

A similar idea was also used in the early models of the American M1 Garand rifle, but was later dropped in favor of a long-stroke piston system, because of some problems with the gas trap mechanism. Many older M1 Garands were retrofitted to use long-stroke piston mechanisms and original rifles using gas trap actions are now very rare and are highly prized models indeed.

The third user of the Bang design was the German Gewehr 41, which was designed to the Wehrmacht's requirement that the rifle should be gas operated, but there should be no hole drilled in the barrel to tap the gases. With this very tight restriction to be met, both the manufacturers (Mauser and Walther) who submitted entries into the competition ended up using the Bang design. The Gewehr 41 was made by both Mauser and Walther and used the same caliber ammunition, but they had other different design features, to meet some of the other requirements of the Wehrmacht. The Mauser design was not as reliable as the Walther design, so the majority were made by Walther. However, the rifle is also very rare today and is very highly prized by collectors.

In all the previous gas-operated actions we've studied, there is a hole drilled into the barrel, near the breech (closed end of the barrel) or the middle of the barrel. The purpose of this hole is to tap some of the hot expanding gases leaving the rifle. This tapped gas is used to operate the mechanism that extracts the old cartridge, loads a new one and also cocks the weapon. In all the previous gas operated systems we studied, the hot expanding gases push the piston or bolt.

In a Gas Trap or Bang system, there is no hole drilled in the barrel. Instead, some of the gases are trapped by a ring-shaped cone at the end of the muzzle (the open end of the barrel). The gases expand into the gas trap and pull a piston (instead of pushing, like the other gas operated actions). Pulling this piston actuates a mechanism to extract the cartridge and reload the gun.

The idea behind this system is that the mechanism to extract and reload the cartridge starts to work only after the bullet has left the barrel. This enhances the accuracy of the weapon.

The problems with the system largely stem from the extra complexities of the gas trap. The gas trap is composed of some very precisely machined parts, which are prone to fouling and corrosion from dirty gases. This makes the system very hard to clean and maintain under normal operating conditions in the field and prone to jamming issues. In the case of the M1 Garand, there were also issues in trying to fit a bayonet on top of the gas trap. This is why the gas trap mechanism never really gained popularity.

Actions: Gas Operated: Direct Impingement

In our last two posts, we studied gas operated actions based upon pistons: the short-stroke piston action and the long-stroke piston action. Now we will study another modern gas-operated action, the direct impingement action. This action was originally invented in 1901, but the first successful rifle to use this action was the French MAS-40, which was commissioned in 1940. Since then, the most famous rifle to use this action is the American M16 family.

Recall that in the two piston driven systems we studied earlier, some of the gases generated by the burning propellant are tapped from the barrel and used to push a piston enclosed within a separate cylinder. The piston in turn acts upon the bolt carrier and bolt and causes them to cycle the rest of the action.

In a direct impingement system, there is no piston, piston rod or cylinder at all. Instead, some of the high-pressure gas is tapped out via a gas tube and piped directly onto the bolt and bolt carrier. The bolt and/or the bolt carrier are fitted tightly into the chamber of the weapon and act as a piston. In the case of the M16 family, the bolt has piston rings fitted to the back in order to provide the tight seal.

Click image to enlarge.

Image is taken from "US Army FM23-9, M16A1 Rifle and Rifle Marksmanship", which is in the public domain.

The bolt and bolt carrier move back due to the gas pressure. While moving backwards, the bolt extracts the fired cartridge case and ejects it via a side port. A return spring pushes the bolt and bolt carrier forward and the bolt picks up a new cartridge from the magazine on the way forward.

The following animation gives a good idea of how this mechanism works:

There are some advantages to such an action. Since there is no piston, piston rod or separate cylinder for the piston and piston rod, therefore the overall weight of the weapon is reduced. Fewer parts also means reduced costs of manufacturing. Since there are fewer and lighter moving parts on the weapon, balance does not shift as much and therefore the accuracy of the weapon is increased compared to piston driven weapons, especially in automatic mode. The gas tube is smaller and lesser mass than a cylinder containing a piston and hence it does not affect the natural resonance of the barrel as much, which also contributes to greater accuracy. Since the moving parts are in the same axis as the barrel of the rifle, this also helps performance when firing rapidly.

The disadvantages of this action are chiefly caused by the hot gases acting directly on most of the operating parts (bolt, bolt carrier, firing pin, springs, extractor etc.). The gases contain some dirty residues, which deposit on the bolt and bolt carrier and will cause reliability issues, if not cleaned frequently. This means that people need to spend more time cleaning and maintaining weapons with direct impingement actions. This also makes the weapon more sensitive to the quality of propellant used in the cartridges. The hot gases also cause the operating parts to expand. Since the parts are tightly fitted and expand at different rates, this could cause jamming and acceleration of wear and tear of the moving parts. Heat from the gases can change the physical properties (hardness, elasticity, brittleness etc.) of the metal parts and cause excess wear. The heat also evaporates the lubricant in the mechanism and this could cause the moving parts to jam up as well.

An infamous case of this is the early problems that the M16 rifles faced. When the original rifle was designed, the ammunition used for testing used a certain type of propellant (a nitrocellulose based powder). However, when the rifle was put into production and sent to the first combat units, the military found that Dupont Inc. could not produce the propellant in sufficient quantities to the specifications demanded. Hence, the ammunition was changed to use a different propellant (a mixture of nitroglycerine and nitrocellulose) which was easier to produce and met the pressure specifications. Unfortunately, this new propellant was dirtier and generated more residue than the one used in the development prototypes. Also to save manufacturing costs, the chrome-lining in the chamber, which was in the prototype design, was removed in the early production models. The early production models were also issued with no cleaning kits or maintenance instructions. These three issues caused many of the early M16s to jam unexpectedly and the rifle earned a very poor reputation during the Vietnam war. After a congressional investigation, the chrome lining was put back and cleaning kits and maintenance instructions were issued and the frequent jamming issues were resolved. While the reliability issues were solved and the M16 had better accuracy than most other competing rifles, the early bad reputation that was earned by the M16 took years to disperse.

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: Gas Operated: Short Stroke Piston

The first gas operated mechanism we will study today is called the short stroke piston. This is the mechanism that is used in rifles such as the American M1 carbine and M14 rifle, the Belgian Fabrique Nationale SCAR assault rifle, the British SA80 assault rifle and the German Heckler & Koch G36 assault rifle.

When a gas operated weapon is fired, the cartridge generates hot gases, which push the bullet out of the barrel. Most of the gas also leaves the barrel behind the bullet, but a portion of the gases are tapped out and used to operate the extraction and reloading mechanism, to eject the old cartridge and load a new one.

The basic idea behind a short stroke piston mechanism is that when the cartridge is fired, some of the expanding gases are tapped by a port close to the firing point or the middle of the barrel. This means that the gas here is at relatively high pressure (compared to if the gas was tapped close to the open end of the barrel). This high pressure gas is then allowed to act upon a piston. The other end of the piston touches the bolt carrier of the rifle. When high pressure gas acts upon the piston face, it pushes the piston back very rapidly, which in turn pushes the bolt carrier back. The piston moves back for a very short distance (generally, a distance that is less than its own diameter) and is then abruptly stopped, either by a projection, or by a gas cut-off. The bolt carrier separates from the piston and continues to move back on its own, due to the kinetic energy imparted to it by the piston. The bolt carrier drags the bolt backwards, which extracts the fired cartridge out and ejects it via a side port. They continue moving backwards and cock the rifle again, ready to fire. When the bolt carrier reaches its most backward position, a return spring pushes it forward again. On its way forward, the bolt picks up a new cartridge from the magazine and pushes it into the firing chamber. As it reaches its forward most position, the bolt locks and the weapon is ready to fire again.

The animation above shows the mechanism of the LWRC short stroke piston mechanism. It only shows the movement of the piston and not the bolt-carrier or bolt, but you can get a good idea of how it works. Note how the hot gases are vented out close to the middle of the rifle.

There are some advantages of the short stroke piston system. Like all gas-operated piston systems, the hot gases only impinge on one side of the piston and the other end of the piston rod pushes the rest of the mechanism. This means that all the hot gases and carbon residue are kept away from the rest of the operating mechanism, which improves reliability and life of the operating parts. Also, since the piston is stopped very quickly, the total mass of recoiling parts is smaller and therefore this makes the weapon easier to control. The other advantage is that shorter barrels can be used with short stroke piston systems.

Actions: Gas Operation: Basics

In the last few posts, we've studied some modern firearm actions such as those that utilize the blowback principle and the recoil operated action. We will now study another family that is also heavily used in modern day weapons, the Gas Operated Action.

The basic principle of this family of actions is as follows: When a cartridge is fired, the propellant material burns and produces pressurized gas. The pressurized gas expands and pushes the bullet out of the front of the barrel. After the bullet is forced out of the barrel, the gas also leaves through the same exit. In a gas operated action, some of this pressurized gas is tapped out from the barrel via a port and used to operate a mechanism to remove the old cartridge, re-cock the weapon and chamber a new cartridge automatically.

The pressurized gas operates the mechanism in one of the following ways:

1. The pressurized gas operates upon a piston, which is forced to move by the expanding gases. The other end of the piston pushes the mechanism that ejects the old cartridge and loads a new one in. The two main types of piston actions are short and long stroke pistons. Piston operated mechanisms are used with weapons such as the M1 Garand, the AK-47 rifle family, the Bren LMG etc. Since the hot high-pressure gas operates upon the piston only, the rest of the mechanism is kept relatively cooler and cleaner, which makes the mechanism much more reliable to operate.
2. Gas trap: This works similar to long stroke piston mechanisms, but uses lower pressure gas to operate. This is a relatively rarer mechanism and was used with the German G41 rifle in World War 2, as well as some early Garands.
3. Direct impingement: Instead of the gas to push a piston, which in turn operates the mechanism, in a direct impingement action, the gas directly acts upon the bolt and carrier. Since there is no piston, this reduces the weight of the weapon and lowers the manufacturing cost. On the other hand, the firing mechanism becomes fouled more quickly and hot gases may also cause the different parts of the mechanism to expand at different rates and thereby lose accuracy. Lubricants in the mechanism also dries up and may cause malfunctions. This is the mechanism used by the M-16, AR-15 and M4 rifles.

Compared to blowback and recoil operated actions, which are used for lower powered pistols mostly, the gas operated action family is primarily used for automatic and semi-automatic rifles.

The first mention of a gas operated action was due to a Mexican General named Manuel Mondragon, who used it in a rifle design called the Mondragon rifle in 1887. It was the world's first semi-automatic and automatic rifle. Due to poor production facilities in Mexico at that time, he tried to get some US manufacturers to make the weapon, but could not garner enough interest at that time. However, he managed to convince the Swiss firm Schweizerische Industrie Gesellschaft (SIG) to manufacture this weapon for him. Excess stock of these weapons from SIG were bought up and used by Germany in World War I and World War II.

The next patent for a gas operated action was filed by the redoubtable American designer, John Moses Browning, who invented a gas operated action in 1889. Browning later licensed his design to Colt in 1892 and it was used to make weapons in a number of calibers.

In the next few days, we will study the various gas operated actions in some detail.