Sunday, October 28, 2012

Self Lubricating Bullets

Your humble editor recently came across an interesting book called "Modern American Pistols and Revolvers". The book dates from 1896 and describes the state of firearms that was considered "modern" in that era. Among its many pages was a mention of something called a self-lubricating bullet.

Self-lubricating bullets seem to have been invented by Daniel B. Wesson, one of the founders of Smith & Wesson. He received a patent for his design in 1893. During this era, fouling in firearms was a big problem because smokeless powders hadn't been invented yet and black powder left a lot residue behind in the barrel. Excessive fouling would cause the finest revolvers in the world to become inaccurate, especially when they were shot rapidly in dry conditions.

Smith & Wesson self lubricating bullet. Click on image to enlarge. Public domain image

In the above image, we see a Smith & Wesson self-lubricating bullet. The bullet has a hollow core in its base, about 1/8th inch in diameter. Inside this core, a copper plug is inserted and the core is filled with lubricant A. The base of the core has a brass plug B. Four tiny passages C are drilled along the side of the bullet and these passages are also filled with lubricant.

Self-lubricating bullet when fired. Click on image to enlarge. Public domain image.

When the bullet is fired, the brass plug B is pushed inside the bullet by the expanding gases, thereby forcing out the lubricant out of the passages C in the conical front of the bullet. The theory was that the lubricant would distribute itself to the walls of the barrel and keep it moist. The black powder residue, which is very hot, would cool down more rapidly because of the lubricant and adhere only loosely to the barrel and could be cleaned easily with only a wire brush.

The book goes on to say that this cartridge was tested by the US Government and seemed to show more accuracy than using regular ammunition, while being slightly more expensive. Smith & Wesson used this idea for several of their cartridges, .38 S&W, .38 Special, .32 S&W, .32 S&W Long, .44 S&W Russian etc.

With the invention of more modern and cleaner burning powders, this type of bullet seems to have lost its popularity.

Wednesday, October 24, 2012

Silhouette Shooting

Silhouette shooting is a sport that had its origins in Mexico and  became popular in the rest of the world after the 1940s. We will study this sport in this post.

The idea behind silhouette shooting is to shoot at metallic silhouettes of animals from various distances. Shooting may be done with black powder rifles, modern rifles, pistols, airguns etc. using a variety of calibers. The targets are shaped like various game animals.

Standard metallic silhouette targets. Click on image to enlarge. Public domain image.

The four target types are chicken, pig, turkey and sheep. Because of the Mexican origin of this sport, the targets are often called by their Spanish names: Gallina (chicken), Javelina (pig), Guajalote (turkey) and Borrego (sheep). The targets are usually made of steel plates and can take several shots. The targets may also be arranged to look left or right.

Multiple targets of each type are placed on the ground and the shooter has to shoot at them in order. A target is considered to be shot if the shooter hits it and knocks it down or pushes it off its stand. Even a shot that bounces off the ground and topples the target over is counted as a hit. If the shooter misses one target, they should take the next shot at the next target. Shooting a target out of order is considered a miss as well. Due to the irregular shape of the targets, it is possible that a shot might pass through without hitting the target, for instance, a bullet could pass through the legs of the pig or the sheep target without touching them. Scores are computed as number of targets hit vs. number of shots fired. The person who hit the most targets with the least shots wins.

Tuesday, October 23, 2012

Testing Black Powder Quality

Back when black powder was the common propellant in use in the 18th and 19th centuries, the power of the powder produced sometimes varied from batch to batch. Hence, it was considered prudent to conduct a standardized test to measure the strength of the black powder in a batch, so that people could calculate how much powder the firearm should be underloaded or overloaded with.

A common device used to do this was the eprouvette. This is a French word and these days it means a "test-tube", but in an earlier era it was used to also denote a device used to test and prove the strength of gunpowder.

The simplest form of this device is a fixed mortar tube, such as the one shown below:

An Eprouvette mortar made of cast iron. Click on image to enlarge.

These were typically made of cast-iron or bronze. The one shown in the image above is only about 5 - 6 inches long, but there were some larger models made as well. The angle of the barrel is fixed at 45 degrees. To test the strength of black powder, a person simply loads the device with a standard amount of powder, then adds a standard weight of shot. Then the person discharges the device and measures the distance that the shot weight flew and compares it with the expected standard distance for the powder.

Of course, with a device such as this, the person conducting the test has to be outside and be able to see where the shot landed, which might be difficult in certain situations. Therefore, people began to invent more portable eprouvette devices.

Three eprouvette devices. Click on images to enlarge.

In devices like the ones above, a standard charge of black powder is loaded into them and then the devices are discharged. The force of discharge compresses a spring, which moves an indicator. In the first two examples, the force of the explosion moves a ratchet gear (the round wheel with teeth) against spring tension. There are markings on the ratchet gear that indicate the strength of the explosion. In the third example, the spring is V shaped and when the tester is discharged, the spring compresses and moves a slider which indicates the force of the explosion.

These devices went out of fashion in the middle of the 19th century as black powder manufacturing quality began to improve. These days, they may only be purchased in auction houses or by manufacturers specializing in period firearms.

Monday, October 22, 2012

How not to shoot a firearm

Remember the discussion we had a long time ago about some bad shooting stances, including the infamous sideways gangsta grip. Recently came across a funny video demonstrating not only the "gangsta grip", but also what the author calls the "modified gangsta grip" and the "super modified gangsta grip".

In case you're wondering, this is a comedy video and demonstrates exactly what NOT to do with a firearm. I hope you guys get as much of a laugh as I did when viewing this.

Thursday, October 18, 2012

Grenades and Firearms: Under Barrel Grenade Launchers

In our last two posts, we studied two different ways to couple grenades with firearms, namely rifle grenades and shoulder fired grenade launchers. Rifle grenades have good range and can be used along with a rifle, but the user cannot simultaneously use it as a rifle and a grenade launcher. Shoulder fired grenade launchers also have very good range, but the user can only use it as a grenade launcher and has to have a small side arm as a backup weapon. The next type of coupling grenades with firearms is the most common one today: the under barrel grenade launcher. We will study them in this post.

Grenade launchers generally tend to have shorter barrels and lower barrel pressures, so it is possible to eliminate the butt stock of a shoulder fired grenade launcher and attach the rest of the parts to the underside of a rifle barrel.

Public domain image of an M4 fitted with an under barrel M203 grenade launcher

In the image above, we have a M203 grenade launcher attached underneath the barrel of an M4 assault rifle. Note that the grenade launcher has its own trigger which is located in front of the M4's magazine. It also has its own adjustable leaf sight, which is the long thin rod in front of the telescopic sight. The leaf sight is used in conjunction with the M4's front sight to launch grenades.

Public domain image of a US soldier using a M203 under barrel grenade launcher attached to the underneath of a M16 assault rifle.
Note how the soldier is using the leaf sight along with the M16's front sight to aim the launcher.

Western made under barrel grenade launchers typically are loaded from the back and the launcher tube either pivots to one side or slides forward to allow the user to load a new grenade cartridge. Russian made grenade launchers are usually loaded from the muzzle.

To launch the grenade, the user typically shifts their hand that is on the rifle's pistol grip to the magazine and then pulls the grenade launcher's trigger. To go back to shooting the rifle, the user simply moves his/her hand back to the pistol grip.

Since the butt stock is shared between the rifle and grenade launcher, this design is much lighter than carrying a rifle and a separate shoulder fired grenade launcher. Unlike rifle fired grenade launchers, the user can walk around with a magazine loaded in the rifle and a grenade cartridge loaded in the launcher and use either at a moment's notice. The user can also easily switch between the two as needed. There are a few disadvantages with this type of launcher though. The first is that the attached grenade launcher alters the balance of the rifle. The second is that these usually don't have as much range as a rifle grenade launcher or a shoulder fired grenade launcher. The third is that these are single shot devices and the user needs to manually reload after each cartridge is fired.

Models such as the US made M203, the German AG36 and the Russian GP-25 and GP-30 are some common under barrel grenade launchers used around the world.

Wednesday, October 17, 2012

Grenades and Firearms: Shoulder Fired Grenade

In our last post, we studied some early developments in grenade launching technology, i.e. the rifle grenade. One of the features of the rifle grenade is that it is built to be used with a normal infantry rifle and some sort of adapter. The user can switch between using the rifle and using it as a grenade launcher. In this article, we will study dedicated grenade launching firearms i.e. devices that are only meant to launch grenades and cannot be used as a rifle.

During the Vietnam war era, the US military developed a dedicated shoulder fired grenade launcher called the M79 for use by troops. The plan was to design a weapon to increase the firepower of troops, while having more accuracy than a rifle grenade, but lighter than a mortar. As a result of this research, the M79 grenade launcher was developed.

M79 grenade launcher. Click on image to enlarge. Public domain image.

It is a simple design that resembles a break-open action shotgun. The front sight at the very end of the muzzle is a fixed type and the rear sight (which is mounted midway on the barrel) is a folding leaf sight.

Even though the original requirement was for a multi-shot launcher, the designers never got that to work reliably and the weapon is a single shot one. This means the user needs to manually load a new cartridge after each shot. This weapon has a range of 75 to 375 meters and can fire a variety of grenade types. It was delivered to the US army in 1961 and quickly became popular among the soldiers, due to its reliability and simplicity. They called it by various names, "Blooper", "Thumper", "Thump-tube" (all due to the sound that it made), "Wombat" (this was its Australian nickname) were all common names. The downside of it was that it was a single-shot weapon and could not shoot rapidly. It also had the problem of being a dedicated device, so the soldier carrying one would only have a small pistol to defend himself.

The South Africans developed a multi-shot dedicated grenade launcher called the MGL. This was developed during 1980-1981 and adopted by their military in 1983. Soon after, it was adopted by other military forces around the world. In US military service, it is called the M32.

US Marine using a M32 multi-shot grenade launcher. Public domain image.

It consists of a six shot cylindrical magazine that resembles a revolver magazine. One major difference though is that the magazine is driven by a spring, so it must be wound back up after reloading. This fires a variety of grenades, just like the M79 does. In fact, one variant is the same caliber as the M79.

In the next post, we will look at some other types of launchers as well.

Monday, October 15, 2012

Grenades and Firearms: Rifle Grenade

In our last post, we studied the origins of the grenade and about those specialized troops trained to use them, the Grenadiers. Towards the end of the last post, we'd mentioned that grenadiers and grenades started to become less useful towards the end of the 19th century, but grenades came back in popularity in the 20th century. We will continue our story from here.

In 1904, as relations between the Russian empire and the Japanese empire broke down, the Russo-Japanese war began. This was the first major war in the 20th century and had modernized troops on both sides. A Japanese colonel named Amazawa started experimenting with grenades fired out of rifles, during the Battle of Port Arthur. In our previous post, we'd mentioned that grenadiers of the previous era were typically the largest and strongest soldiers because they needed to throw the grenade for a considerable distance. A rifle fired grenade made it possible for weaker soldiers to use grenades too, by using a firearm to launch the grenade instead of throwing it.

The idea of using a firearm to launch a grenade is actually an old invention and was not of Japanese origin. In the School of Infantry Museum in Warminster, England, there is a flintlock musket called the "Tinker's Mortar", which dates back from 1681. This unusual musket has a cup built into the buttstock. To use it as a launcher, the user would first place the rifle with the muzzle on the ground, then pour a propellant charge into a special chamber under the the cup. A channel ran from the flintlock pan to the cup. A grenade with a fuse was placed inside the cup. When the powder in the pan was lit, the pressure of the burning propellant would launch the grenade and the flash would also simultaneously light the fuse as the grenade was pushed out. This was a very cumbersome device, so the idea of a rifle launched grenade was generally shelved in the west for a few centuries. It was the work of Colonel Amazawa in Japan that restarted interest in this subject again. As it turned out, a number of observers from every major western power were watching the course of events of the Russo Japanese war and this is how the concept returned back to Europe.

In 1907, a Britisher named Martin Hale invented a rod grenade, followed by other inventors with similar ideas from Germany, France, Austria etc.

A Mills bomb Number 23 Mk 1 rod grenade. 
Image licensed under Creative Commons Attribution-Share Alike 3.0 Unported license by Jean-Louis Dubois

The concept of a  rod grenade is simple. It consists of a specialized grenade with a simple steel rod attached to it. The rod is inserted into the barrel of the rifle and a special blank cartridge is chambered into it. The rifle butt is placed on the ground. The user holds the grenade's safety spoon with one hand and removes the safety pin with the other. The user then places the hand that removed the safety pin back on the rifle's grip, then released the hand holding the safety spoon and places it on the fore stock and fires the rifle as quickly as possible.

This idea was used from 1907 to the early stages of World War I. While it worked decently in theory, there were some practical issues with it. On the good side, it enabled users to launch grenades at longer distances than was possible before. However, after repeated firing of grenades with this method, the rods tended to damage the rifle's barrel. If the user didn't move fast enough after releasing the safety spoon, the grenade could end up exploding on the user's face. If the user was suddenly faced by an enemy close by, the rifle was unusable as a firearm, as the user would have to remove the grenade from the muzzle, re-insert the safety pin back into the grenade, remove the blank cartridge and then chamber a normal round before he could use the rifle to shoot at his enemy.

In order to fix the issue with the rods damaging barrels and the need for the user to quickly launch the grenade after releasing the safety spoon, a cup-type rifle grenade launcher was invented in the middle of World War I. With this, a standard hand grenade could be used. The user would remove the safety pin and place the grenade in the cup launcher. The cup held the grenade's safety spoon in place until it was launched. The user would then place the rifle butt on the ground, load the rifle with a special blank cartridge and then fire it. This type did not wear out the barrel like the rod grenades did and also, the user didn't have to fire the weapon right away, as the cup would hold the grenade's safety spoon in place until it was fired. It also could use standard hand grenades, which meant the soldier didn't need to carry two types. The only disadvantages are that it required the user to use a special cup adapter and a special blank cartridge to shoot grenades, which could leave the user vulnerable if he was surprised by an enemy when preparing to fire one.

The next development was by the French and was called the "Vivien et Bessiers" shoot-through grenade named after its inventors, Vivien and Bessiers, (otherwise called VB grenade). This built on the concepts of the cup-type rifle grenade, but did not require a special blank cartridge to launch. Instead, this type of grenade has a hole in the middle, that allows a standard rifle bullet to pass through it. As the bullet passes through the center, it arms the grenade. The grenade is then launched by the hot expanding gases coming out of the barrel. So all that the user has to do is place the grenade on the cup and then use a standard rifle bullet to launch it. While this type did not require special blank cartridges, it still required a special cup adapter to use.

Another type of grenade is the bullet-trap type, which traps the bullet instead of letting it pass through and uses its momentum to carry the grenade into the air. Like the shoot-through grenades, the user can use a normal cartridge to launch the grenade and has no need to carry blank cartridges. This type does not require any special cup adapter unlike the shoot-through type.

A French APAV40 grenade (green) at the end of a FAMAS rifle. Click on image to enlarge
Original file was licensed under a Creative Commons Attribution-Share Alike 2.0 license by Rama at wikipedia.

In the above picture, we have a bullet-trap type French APAV40 rifle grenade (the green part). This can be used for both anti-personnel and anti-vehicle applications. The user merely places it on the muzzle of any NATO rifle (such as the French FAMAS rifle) and pulls the trigger. The impact of the bullet striking the bullet trap and the expanding gases serve to arm the grenade and launch it in the air. The grenade has a mechanism that allows it to explode on impact. Larger bullet trap types such as the French AC58, the Belgian & Leichtenstein ENERGA grenade and the American M31 HEAT were designed to be used against armored vehicles.

Rifle grenades have the advantage of having the maximum range of all firearm launched types and modern designs do not require any special adapter or ammunition to launch them. Also, the rifle's balance and weight are not affected as some other designs which we will study shortly. The disadvantage is that if the user wants to launch a grenade, he must mount it to the muzzle before every shot. If he is surprised by an enemy at close range while preparing to fire a grenade, he cannot easily respond with his rifle, as it takes some time to take out the grenade and prepare the rifle to shoot normally.

In our next post, we will study some more developments of using firearms to launch grenades, including dedicated grenade launchers.

Sunday, October 14, 2012

Grenades and Firearms: Basic History

A grenade is a weapon with a long history and in recent years, it has been combined with firearms to produce rifle-launched grenades, under barrel launchers etc. We will study how this came to be in the next series of posts.

The word "grenade" is based on the French word for the pomegranate fruit, as some early grenades used to have the same basic shape as the fruit and the shrapnel inside resembled the seeds of a pomegranate.

It may come as a surprise to some to discover that grenades were in use before the invention of gunpowder! The very first grenades were clay pots that were filled with incendiary material such as petroleum and Greek fire (the method and ingredients for making Greek fire were closely guarded state secrets and the formula has now been forgotten, but we know from ancient historical documents that it was a very flammable liquid and could continue to burn on top of water.) These grenades first appeared on the scene in the Eastern Roman empire (i.e. Byzantine empire) around 740 AD or so. Later on, glass containers were also used instead of clay pots.

Ancient Grenades. Click on image to enlarge.
Image licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License by user badseed at Wikipedia.

People would fill containers like these with petroleum or Greek fire, seal the hole on top and then tie a burning rag and throw them. Upon hitting a hard surface, the container would shatter and spill its contents around an area and the contents would then ignite from the flame on the burning rag, thereby causing havoc over a small area. This idea later spread to Muslim areas during the crusades and from there on, it worked its way into China by the 10th century AD.

Meanwhile, the Chinese had also discovered gunpowder at around the same time and soon after, they began packing it into their grenades. A military manual called Wujing Zongyao ("A Compilation of Military Classics") written in 1044 AD describes a gunpowder recipe to be used with a grenade. About three hundred years later, the Chinese began to make their grenade shells out of cast iron rather than clay or glass for greater effect. This was mentioned in the Chinese Song dynasty era book Huolongjing ("Fire Dragon Manual") written in the 14th century, which describes various gunpowder based weapons in use in China during that period. One of the formulas that the author recommends is a mixture of tung oil, urine, sal ammoniac, feces and scallion juice to be heated and then coated upon tiny iron pellets and bits of broken porcelain. The pellets are then put in a cast-iron container loaded with gunpowder and then launched either by hand or catapult. Anyone unlucky enough to be hit by this shrapnel would die slowly from blood poisoning, if they were not killed outright.

The cast-iron and gunpowder design slowly started to move back westwards from China to Europe and in the 17th century, European countries were using cast-iron gunpowder based grenades as well. The word "grenade" to describe the weapon was first recorded in use in 1688 during the Glorious Revolution, though it is possible that they were in use in Europe some decades before in Austria and Spain.

As the Europeans began to use the grenade, they also developed specialized troops trained to use these weapons. Such troops were called "Grenadiers" and the first official grenadiers were in the army of King Louis XIV of France.

A grenadier belonging to Emperor Napoleon's guard. Click on image to enlarge. Public domain image.

Since a grenade lays damage about a large area, it was necessary for a grenadier to be able to throw it far away as possible in the direction of the enemy and away from one's own troops. This meant that the grenadier had to be a person who was taller and stronger than average. A grenadier also had to be brave and disciplined enough to stand up in the front of the line, light the fuse of his grenade, wait for the fuse to burn down and then throw it at an appropriate time so that the enemy could not throw it back. Only the largest and strongest soldiers were chosen as grenadiers and they were given more training than the average soldier. The grenadiers were therefore regarded as the elite assault troops of their era and had higher pay and wore special uniforms to show their status.

By the 19th century, the use of grenadiers to throw grenades had become less useful, but such large imposing soldiers were also used to lead dangerous assaults on the battlefield.

The revival of grenades in warfare and using firearms to launch them (so that weak people could also launch them for a longer distance easily) began with the Japanese in 1904, but that is a subject for the next chapter, where we will study how firearms and grenades started to become integrated.

Saturday, October 6, 2012

Firearm Malfunctions: How to Clear Them

In the last few posts, we've studied various forms of firearm malfunctions. In this post, we will study some procedures for fixing them.

So what should a person do when they encounter a firearm malfunction?

Step 1: This is the most important part. Identify the type of malfunction and decide if it can be fixed immediately or not. Some firearm malfunctions can be handled by the user immediately, others may need a trip to a qualified gunsmith to fix it. For example, if a stovepipe malfunction should occur, then the user can easily clear it right away and continue shooting. If a misfire occurs, then the user should keep pointing the gun in a safe direction for a little while, in case it is a hangfire and not a dud cartridge, before attempting to fix the problem. If the previous cartridge shot was a squib, the user should stop firing immediately and unload the gun and make it safe for transport to a location where the stuck bullet may be removed.

Step 2: If the malfunction can be fixed immediately, the user should perform the appropriate procedure for clearing the firearm. For instance, with a pistol, a stovepipe malfunction or a failure to feed may easily be handled by a standard tap-rack-bang drill (we'll discuss this shortly). In case of a double-feed issue, a more thorough clearance drill should be used (we'll discuss this as well in just a few moments). For some failure to extract issues, it may be necessary to take it to a gunsmith rather than try to fix it in the field.

Step 3: If the malfunction continues to reappear, there may be some problem with the firearm. In this case, it would be a good idea to stop using the firearm in question. The firearm may require a thorough cleaning to fix the problem or it may be necessary to take it to a gunsmith.

We talked about the tap-rack-bang drill and the clearance drill just a couple of paragraphs above. So how does one perform these drills? Here's a video from Clint Smith, director of Thunder Ranch, demonstrating both drills:

Viewers may note that the first malfunction he clears was actually two malfunctions in one, where it was a failure to feed due to a loose magazine as well as a stovepipe malfunction :).

Happy viewing!

Thursday, October 4, 2012

Firearm Malfunctions: Slamfire

In today's post, we will look into another type of firearm malfunction called the slamfire.

When a new cartridge is being loaded into the firing chamber of the firearm, sometimes the bolt slams the cartridge into the chamber with such force that the weapon fires without the user having pulled the trigger. This is known as a "slamfire".

A slamfire is particularly dangerous because it happens when the user is usually not expecting it to happen. In some firearms, it can happen even with the user's finger off the trigger and the safety enabled. In the case of semi-automatic and fully-automatic weapons, it may cause them to keep shooting until the magazine is empty. Since a slamfire comes as a surprise to the user, it may cause the user to lose control of the firearm and point it in an unsafe direction.

Slamfires are more common in weapons which have a free-floating firing pin, than in weapons which have a spring-loaded firing pin. When a semi-automatic or an automatic firearm is fired, the hammer strikes the first cartridge loaded and causes it to explode and push the bullet of the barrel. Some of the recoil force is harnessed to reload the firearm automatically. The recoil force pushes the bolt backwards and as it moves back, an extractor claw pulls out the cartridge that was just fired. The bolt continues to move backwards and compresses a return spring. Meanwhile the extractor claw pulls the empty cartridge case backwards until it can be pushed out via the ejection port. Meanwhile the bolt moves to its backward most point and is then pushed forward again by the compressed return spring. On the way forward, it picks up a new cartridge from the magazine and pushes it into the chamber. As the bolt reaches the chamber, the firing pin continues to move forward due to inertia, until it is stopped by the cartridge's primer. Now if the firing pin is spring loaded, the spring slows down the firing pin so that it doesn't slam against the cartridge's primer so hard. However, if the firing pin is free-floating, then there is nothing to slow it down as it slams into the cartridge's primer. In either case (but especially for free-floating pins), there is a chance that the firing pin slams into the cartridge primer a little harder than expected and could cause it to detonate prematurely. This causes the firearm to discharge without the user pulling the trigger and then the cycle repeats.

Free-floating firing pins are more common with military firearms, so there is a greater chance of slamfires occurring with them. Of course, this is not to say that firearms with spring-loaded firing pins are immune to slamfires, because it can happen with them as well, but not as often as those with free-floating pins.

As you can see on the above video, the Tavor accidentally slamfires at 0:24 after the user switches magazines.

Slamfires can also happen on some bolt action firearms, when the user is manually cycling the bolt and pushes it forward a little too hard.

In the above video, a slam fire happens as the user chambers the 3rd cartridge on a Stevens bolt-action rifle.

The main causes for slamfires to happen are:
  • Dirt and corrosion: If enough dirt gets in the bolt's firing pin channel, then it could cause the firing pin to stick to the bolt wall and protrude out of the bolt, which could cause the slamfire to happen. The same thing could happen if corrosion causes the firing pin to protrude out of the bolt.
  • Ammunition: Some ammunition is manufactured with more sensitive primers than others and require less force to detonate. This could cause slamfires.
The solutions to fix this are fairly simple: 
  • The first solution is to keep the firearm clean to prevent dirt from jamming the firing pin. 
  • The second solution is to use cartridges with less sensitive primers so that more force is needed to detonate them. This is why military cartridges usually have harder primer caps so that they need an actual hammer strike on the firing pin, rather than inertia, to detonate them. 
  • The third solution is to design the firearm to minimize slamfires. For instance, the firing pin could have a spring around it, so that it slows down the firing pin as the bolt slams forward. The spring provides enough resistance that the pin will not hit the primer hard enough due to inertia, but will detonate the cartridge when the back of the firing pin is struck by the hammer.
  • A fourth solution is to make the firing pin as light as possible, so that it doesn't transfer enough force to detonate the primer due to inertia.
Some models of firearms are more susceptible to this problem than others. For instance, the Russian SKS rifle is notorious for this behavior (as is the Chinese-made Norinco SKS clone). The main reason is because dirt tends to build up near the firing pin channel and jams the pin stuck. Good regular cleaning around the firing pin keeps the problem down. The problem can also be remedied by replacing its free-floating pin with a relatively cheap spring-loaded firing pin replacement, but it is impossible to see if this modification was done or not by merely looking at the rifle. This is why some firing ranges don't allow shooters to bring SKS rifles in for this reason.

The above video shows a SKS slam firing, the reason why it slamfires and a replacement firing pin that fixes this problem, demonstrated by Ben Murray, the inventor of the replacement firing pin himself. Note that due to slamfire, the SKS fires multiple rounds one after another continuously like a fully-automatic rifle, even though it is actually designed as a semi-automatic rifle and it manages to do this despite the facts that the user's finger is off the trigger AND the safety is enabled! This shows how dangerous slamfires can be, especially when the user is not expecting it.

The Tavor TAR-21 reportedly had a slamfire problem when using some brands of commercial ammunition available in the US, until Israel Arms replaced the free-floating firing pins with spring loaded pins free of charge. The reason this happened was that the TAR-21 was originally designed with military ammunition in mind, which have harder primer caps. The Fabrique Nationale FS2000 semi-automatic carbine also had this same problem with certain brands of commercial ammunition available in the US, causing FN Herstal to recall this model in 2006. The FS2000 came with a firing pin that was originally designed for the military FN F2000 carbine and was therefore heavier, so that it could work with the heavier primer caps of military ammunition. With certain brands of commercial US ammunition with more sensitive primers, the firing pin was heavy enough to detonate them via inertia alone.

There are some pump-action shotguns that are deliberately designed so that they can slamfire if the trigger is held down and the pump is operated. Examples of this include the Winchester model 1897 and Ithaca model 37 shotguns.

This feature is useful for a soldier to rapidly fire into an area (such as a trench or a tunnel), which is why SEAL units in the Vietnam era carried the Ithaca 37 into action.

Firearm Malfunctions: Failure to Eject

In our last post, we looked at a particular mechanical malfunction called Failure to Extract. In this post, we will look at a related malfunction called Failure to Eject.

In a Failure to Eject type malfunction, the old cartridge shell is properly extracted from the chamber after it is fired, but due to some reason, it doesn't get ejected out of the ejection port and stays in the gun partly. Because of this, the slide cannot close and the gun gets jammed. We've actually already studied one type of Failure to Eject last month: The Stovepipe Jam.

A pistol jammed by a stove pipe jam (A Failure to Eject type malfunction).
Click on the image to enlarge.

As can be seen in the picture above, the empty cartridge case was not fully ejected out of the firearm and got caught in the slide, thus preventing it from closing fully and therefore leaving the pistol jammed.

As far as the reasons why this happens, the big reasons are:
  • Dirt: Buildup of dirt or corrosion near the magazine spring, return spring or extractor can cause it to fail to eject.
  • Limp wristing of weapon: We already studied the subject of limp wristing a couple of months ago. By not holding the firearm strongly enough and not offering enough resistance and rigidity to the recoil forces of the firearm, the firing action may not complete its cycle properly and hence a jam occurs. This is more commonly seen when using pistols and is usually the #1 cause of failure to eject.
  • Defective ammunition: The propellant in the cartridge case may have degraded sufficiently due to age, or the cartridge may not have been filled with enough propellant. Either way, the burning propellant doesn't generate enough power to cycle the action properly and so the cartridge doesn't get fully ejected by the time the slide returns back.
  • Faulty ejection mechanism: Either the return spring of the slide may be too strong or the magazine spring that ejects the old cartridge is too weak. In either case, the slide moves back and then gets pushed forward and starts to close before the old case is ejected. Therefore, the old case gets caught before it has a chance to fully leave the firearm. The ejector may also be damaged (this is the piece that is near the back of the empty cartridge's movement, which pushes the empty cartridge out towards the ejection port), which may cause it to fail to push the shell out.
  • Spin back The old cartridge case does get ejected, but it hits something on the way out (e.g. the ammunition belt, or the drum, or the side of the ejection port) that causes it to spin back into the ejection port instead of going out of the weapon. Some rifles are more susceptible to this than others: e.g. the Stoner 63A, which was used by SEALs in Vietnam, occasionally suffered this when configured with a snail-drum magazine which fed from the left hand side. It did not exhibit this issue when configured with a box magazine fed from the right hand side.
Remedying this problem in the field is fairly easy as the stuck empty cartridge is usually easy to remove without using any tools. The primary cause of this problem in handguns is because of limp-wristing. However, if the problem continues to happen, then the extractor, ejection spring or return spring (or more than one of the above) may need to be replaced.

Tuesday, October 2, 2012

Firearm Malfunctions: Failure to Extract

In our last post, we looked at one of the mechanical malfunctions that can happen to a firearm, namely Failure to Feed. In this post, we will look at another type of mechanical malfunction, namely Failure to Extract, otherwise known as FTE.

A "Failure to Extract" occurs when the slide or bolt move backwards, but the empty cartridge case remains behind in the chamber. In this situation, a new live cartridge may sometimes be forced into the base of the old case and the slide stays open and the firearm becomes jammed. This is called a "double feed". When this happens, the firearm can be difficult to clear.

Failure to Extract. Click on image to enlarge.

In the above image, we see a failure to extract, which causes a second cartridge to "double feed" into the chamber and leave the slide opened. The magazine may get stuck and refuse to drop out of the weapon. This type of jam sometimes requires some tools to clear the problem.

There are a few reasons why this can happen:

  • Dirt and corrosion: This is the #1 reason for failure to extract. Dirt or corrosion in the extractor claw or firing chamber can cause the empty cartridge to not be picked up correctly.
  • Damaged extractor: A damaged or bent extraction claw may not pick up empty cartridges correctly. A weak extractor spring could also cause this malfunction to happen.
  • Defective cartridge: Due to damage around the cartridge rim, the cartridge may slip off the extraction claw and remain behind in the chamber. Bulges in the cartridge could cause excess friction on the sides, which causes the cartridge to slip off the extraction claw.
A failure to extract will cause the weapon to not fire any more, until the problem is cleared. The cost of fixing this is usually not that much, as cleaning dirt is a standard procedure that should be carried out with any firearm. Damaged extraction claws and extractor springs can also be replaced fairly cheaply, as these parts are not that expensive for most firearms. Defective cartridges can be disposed off and cartridges of better quality can be purchased instead.

Monday, October 1, 2012

Firearm Malfunctions: Failure to Feed

In our last post, we looked at firearm malfunction due to squib loads. In the article previous to that, we looked at malfunctions due to hang fires and dud cartridges. All these are classified as problems caused by faulty ammunition. In the next few posts, we will look at malfunctions due to mechanical problems. The first of these malfunctions we will look at is Failure to Feed, otherwise known as FTF.

Briefly, "Failure to Feed" is defined as when the weapon fails to feed a cartridge into the firing chamber for some reason. In a semi-automatic or an automatic weapon, this means that the cartridge does not properly travel from the magazine to the chamber and the slide remains partially open. When this happens, the weapon is said to be "out of battery".

There are several reasons why a firearm could fail to feed a cartridge:

  • Dirt: Accumulation of dirt in the firing chamber, bolt or bolt carrier can cause the cartridge not to sit properly inside the firing chamber.
  • Damaged magazine: If the magazine has dents, bulges or damaged lips, these may cause the cartridge to be misaligned as it is being fed into the chamber. A weak magazine spring may also cause failures to feed.
  • Improperly loaded magazine: The magazine could be in good shape, but it may not be pushed all the way into the firearm, which may cause the cartridges to not enter the chamber correctly.
  • Damaged cartridge: Sometimes the cartridge may have dents or bulges in it which could cause a failure to feed, as the slide may not pick it up correctly, or it may not fit into the chamber tightly because of dents or bulges.
  • Riding the slide: This is when the user holds the slide as it is moving forward and impedes its speed. When this happens, the slide may not have enough momentum to properly seat the cartridge in the chamber. The user should pull the slide back as far as it will go and then let it go and let the recoil spring do the job of loading the next cartridge.
In most cases, a failure to feed can be easily fixed. For instance, dirt in a firearm can generally be cleaned fairly easily, an improperly loaded magazine can be pushed into place, damaged cartridges can be removed from the magazine and discarded etc. All these are easy for the average user to do and not expensive at all. In other cases (e.g.) damaged magazine or weak magazine springs, the magazine may need to be replaced, or it may need to be sent to a gunsmith for repair. The cost of replacing a magazine is usually affordable (e.g. about $20-$30 or so) in most cases.