Friday, July 18, 2014

Ammunition Belts

We have been talking about magazines in the last few posts. In today's post, we will look at something that is not quite a magazine, but definitely holds ammunition. In today's post, we will study ammunition belts.

While an ammunition belt can hold and feed cartridges into a firearm, it does not fall into the category of "magazine", because it has no feeding mechanism of its own. Instead, an ammunition belt relies on a separate feed system built into the rifle, to extract and use the ammunition. Belts are generally used with firearms that have a high rate of fire (e.g.) machine guns.

An M60 machine gun with an ammunition belt. Click on the image to enlarge. Public domain image.

Early ammunition belts were made of cloth, with evenly spaced pockets to place cartridges into. These were used in early machine guns, such as the Maxim gun, Vickers machine gun, Browning M1919 machine gun etc. The feed mechanisms on these early guns are designed to pull each cartridge from a belt backwards and then feed the cartridge forwards into the chamber. The empty belt is pushed out of the other side of the gun and it may be refilled again. The good thing about cloth belts is that they are easily reusable and can be quickly refilled. The problem with cloth belts is that they tend to be somewhat prone to jamming, especially because cloth tends to deteriorate if it absorbs water, oil, cleaning chemicals etc. Also, the empty side of the belt may get tangled up with vegetation and debris as it comes out of the gun. This is usually a problem, if the gunner wants to move the gun.

An ammunition belt made of cloth.

Because of the jamming issues, ammunition belts are now generally made of metal links. Metal links have the advantage that they are not affected so much by oil or cleaning solvents. However, they tend to be heavier than cloth belts.

Newer ammunition belts are made using disintegrating metal links. What this means is that each link is connected to the round ahead of it in the belt. As each cartridge is stripped out of the belt and loaded into the firearm chamber, this causes the link holding the cartridge to fall out of the belt and the link can be ejected out of the bottom of the gun. This means that there is no empty belt coming out of the other side of the gun and it can't tangle up with anything. Therefore, the operator can move the gun without worrying about a half-empty belt dragging on the ground. On the other hand, disintegrating belts are not as easy to reload as non-disintegrating types.


The above video shows a user using a belt with disintegrating links. As you can see, the links holding the ammunition fall out of the gun as each cartridge is fired and there is no empty belt coming out of the side.

In general, cloth belts are cheaper to manufacture than metal belts and more flexible, but are also more prone to getting affected by rain, oil, cleaning solvents etc. Metal belts are more expensive to manufacture, but are more reliable, especially in bad weather conditions.

Belts allow the user to carry a lot of ammunition and are relatively lightweight. This is why they are used on firearms with high rate of fire (e.g.) machine guns. Many machine guns have a box on the side, where a folded belt may be placed. The picture of the M60 above shows one such ammunition box. This allows the user or an assistant to conveniently carry ammunition around and also provides the belt some protection from rain, snow, mud etc.

Monday, July 14, 2014

Turret Magazines

In our last post, we looked at horizontal magazines. In today's post, we will look at a type of magazine that was used in the 19th century: the turret magazine.

During the middle of the 19th century, Samuel Colt perfected the revolver and obtained patents for revolver cylinders. Hence, anyone who attempted to make a revolver type firearm during that period, was likely to infringe on his patents and would have been forced by law to not manufacture such weapons. Turret magazines were seen as one way to bypass Colt's patents.

Turret magazines are simply drums where the cartridges are placed facing radially outwards. There were two types of turret weapons developed: horizontal turrent firearms and vertical turret firearms. In the horizontal turret firearm category, we have a few examples shown below:

A Daniels Turret Rifle. Click on the image to enlarge




A Cochran revolver shown with turret magazine loaded and unloaded. Click on the images to enlarge

In the above pictures, we see some firearms with horizontal turret magazines. As the reader may note, the magazine is horizontally positioned on the firearm. Percussion caps are placed on the nipples at the underside of the turret magazine, to ignite the gunpowder loaded into the chambers. Note that in the above examples, the hammer of the firearm is placed under the firearm and in front of the trigger and the magazine is accessed from the top. The pictures of the Cochran revolver, in particular, show how the magazine is loaded and unloaded from the top of the firearm. John Webster Cochran of New York, received about 25 different firearm patents and was well known for his "recoil-free" turret weapons. Many of his turret designs were manufactured under license by the company of C.B. Allen of Springfield, Mass.

There is also the vertical turret magazine and in this category, we have:

Porter turret rifle with spare magazine. Click on the image to enlarge.


Porter turret rifle, showing how the magazine is loaded. Click on the image to enlarge.


A French made Goudry turret revolver, open and closed. Click on the images to enlarge.

Porter turret rifles were invented by T.P. Porter and were seen as competitors to Colt's revolving rifles. They were used by many pioneer settlers moving towards the Western United States. Turret magazines hold about 9-20 cartridges, which is pretty high capacity for the period that they were used.

Both horizontal and vertical turret weapons are somewhat dangerous, because a loaded weapon will always have at least one of its cartridges pointing directly back at its user. After firing a cartridge, there is the danger of stray sparks flying into other chambers and a chain fire discharging the other chambers as well. This actually happened on some occasions and resulted in fatal accidents. Samuel Colt, being a crafty businessman, took full advantage of this news and advertised that his revolving system was much superior and reliable compared to any turret firearms. In fact, Colt even falsely spread a rumor that the inventor of the Porter rifle (T.P. Porter) was killed when demonstrating his own rifle to customers! These news items and rumors had the effect of halting sales of Porter rifles and turret magazines in general and Mr. Porter spent the rest of his life making more traditional firearms.


Tuesday, July 8, 2014

Horizontal Magazines

In today's post, we will study a type of magazine that has been used on only a few firearm models so far. Today's subject of study will be the horizontal magazine.

One of the well known weapons to use the horizontal magazine is the Fabrique Nationale FN P90 personal defence weapon.


The transparent piece lying flat at the top of the weapon is the horizontal magazine. In the above image, the cartridges emerge out of the magazine on the right side. The picture below shows what the magazine looks like, when it is detached from the firearm:

A horizontal magazine. Click on the image to enlarge.
Image released under a Creative Commons Attribution-Share Alike 3.0 Unported license by ROG5728

It consists of two rows of cartridges in the magazine, which lie at right angles to the barrel, when the magazine is attached to the firearm. A spring at the back of the magazine pushes the cartridges out towards the feed lips (the opening at the circular part in the image above) of the magazine. Near the feed lips is a stationary spiral ramp that combines the two rows of cartridges into a single row and also rotates the cartridges by 90 degrees as they emerge out of the magazine, thereby loading into the chamber with the proper orientation. The magazine is made of a translucent plastic material, allowing the user to see how many cartridges are left in the magazine. An FN P90 magazine can hold 50 cartridges when fully loaded.

Public domain image of the FN P90 magazine patent. Click on the image to enlarge.

The above image shows some of the details of the magazine, taken from one of the pages of the patent claim. This particular magazine design was invented by Rene Predazzer and the full details of the patent claim may be found here. Figure 6 in the image above shows how the double rows of cartridges are combined into a single row by the ramp and rotated before exiting the feed lips.

Another firearm that uses a horizontal magazine is the AR-57, which is basically a firearm with an AR-15/M16-style receiver chambered to use the FN P90 cartridges and horizontal magazine. This was designed by Rhineland Arms Inc.

However, the FN P90 is not the first user of a horizontal magazine. There exists an US patent claim from 1923 by Arthur Kottas, a retired officer of the Austrian Army, where a horizontal magazine is described (in fact, his US patent claim mentions that he first patented his invention in Austria on August 16th, 1918, so the actual invention date is even earlier). The details of his patent may be found here:

Public domain image of Arthur Kottas' magazine design from 1923. Click on the image to enlarge.

In the Kottas patent, a single row of cartridges is placed at right angles to the barrel and rotated into position before entering the chamber.

There also exist other US patent claims from 1948 by Woodville B. Conway (details may be found here) and in 1953 by John L. Hill (details may be found here).

Public domain image of John L. Hill's patent from 1953. Click on the image to enlarge.

In both the Conway and Hill patents, note that the magazines contain double stack of cartridges which are combined into a single stack and then rotated before exiting the chamber. The same double stack idea is used in the FN P90 magazine as well, except that the magazine is placed at the top of the firearm instead of underneath it.

The nice thing about horizontal magazines is that they can contain a large number of cartridges for their size. For instance, the FN P90 magazine can hold 50 cartridges, which is pretty amazing considering the size of the firearm. Also, compared to a box magazine which projects out of a weapon, this type of magazine sits horizontally and flat inline, which makes the firearm much more balanced and convenient to hold. Since the magazine stores cartridges side by side, it can safely be used with centerfire cartridges using spitzer-type bullets. In the case of the FN P90, the magazine is made of a semi-transparent plastic, which allows the user to see how many cartridges are left in the magazine.

Tuesday, July 1, 2014

Helical Magazines - II: The Evans Rifle

In our previous post, we'd studied the helical magazine, as invented by Calico Inc. in 1985. However, there is a precusor to this that was invented in the 19th century, called the Evans Repeating Rifle, that also used a helical magazine of sorts. We will study that particular rifle in today's post.

The Evans rifle was invented by Warren R. Evans, a dentist from the state of Maine. He received his first patent for an improved magazine in December 1868 and another patent for an improved gun lock in 1871. With these two patents, he entered his prototype rifle into the US Army trials of 1872, but his rifle was not selected due to mechanical issues. However, he wasn't the only mechanically inclined person in his family and his brother, George Franklin Evans, was also a talented machinist. He and his brother joined forces with a few other investors and started the Evans Rifle Manufacturing Company in Maine in 1873, to manufacture this rifle design for the commercial market.

An Evans Repeating Rifle

This rifle is a lever-action firearm and the trigger guard doubles as the lever that operates the action. Like the Spencer rifle (which we studied earlier here and here), this rifle also has a magazine inside the stock. However, the Spencer rifle has a tubular stock, whereas this rifle has a helical type feed mechanism that uses an Archimedian screw (The screw gets its name from the fact that it was supposedly invented by Archimedes, but was actually invented by Assyrians about 350 years earlier. It was used for pumping water in the ancient world). In the case of the Evans rifle, the screw thread is used to push cartridges into the chamber.

Disassembled Evans Rifle Magazine.

The above image shows a disassembled Evans rifle magazine. The barrel is  facing to the left and the two halves of the magazine occupy most of the picture. The screw thread can be clearly seen inside the magazine. Unlike the helical magazine that we studied in the previous post, this one is not spring loaded. Instead, upon operating the trigger guard lever, the screw rotates 1/4th of a turn, which pushes the next cartridge into the chamber.

Like the Spencer rifle, new cartridges are pushed in from the base of the buttstock. Unlike the Spencer rifle's tubular magazine, this is safe to use with centerfire cartridges using spitzer type bullets because the tip of each bullet does not touch the primer of the previous cartridge. The Evans rifle holds 34 cartridges in its magazine, compared to the Spencer's seven cartridge tubular magazine and the Winchester M1873, which holds 15 cartridges in its tubular magazine.

About 12000 to 15000 rifles were manufactured by the company during its existence. Evans rifles were given to several foreign military officers and politicians and were also endorsed by celebrities of the day, such as Kit Carson and Buffalo Bill Cody. In fact, Kit Carson even enthusiastically submitted the following testimonial to the Evans company, saying: "At twenty paces, have, with this rifle, shot the eyebrows from my wife, and every night regularly, in the presence of an audience I shot an apple from her hand, a pipe from her mouth, a penny from her fingers, or snuff a candle from her hand. I think the Evans is the safest and most complete repeating system ever devised."

An enthusiastic endorser of the Evans rifle. An Apache Indian holding an Evans rifle from around 1880. Public domain image.

However, there are a few disadvantages of this design as well:

 The first is that the new cartridges are loaded through the butt plate, not the front of the magazine (unlike the Calico helical magazine that we studied in the previous article). This means that if the user loads a single cartridge into the magazine, he (or she) has to pull the lever 33 times so that the cartridge works its way through the magazine into the chamber.

Another issue is that the lever controls both the feeding and loading of the magazine at the same time. This presents problems when trying to refill a partially filled magazine On other firearms, such as the Winchester M1873 with a tubular magazine, or the Calico submachine gun, the magazine feed is independent of the action. Therefore, if the user fires (say) three cartridges, the user can then simply push in three more cartridges and top off the magazine. On the Evans rifle, if the user has a fully loaded rifle, then fires three cartridges and then wants to top off the magazine, the user must pull the lever each time a new cartridge is pushed through the butt plate to load the magazine. This means that loading three cartridges through the butt plate will eject three more cartridges from the top of the magazine and there will be a gap in the magazine before the last three cartridges can be fired. The only way that a user can always keep the magazine topped off is by firing a single cartridge, then pushing a new cartridge into the butt plate and operating the lever to eject the old cartridge case and load the new cartridge into the magazine. This problem was later partially solved by George Evans in 1877, by making a design modification that allowed the user to load the rifle from from the breech end, without disturbing the cartridges already in the magazine.

This rifle also uses specially designed cartridges (the .44 Evans Short and .44 Evans Long for later models), which were not used by any other firearms and were not easily available either. The only manufacturer of this ammunition was the Evans Rifle Manufacturing Company themselves and they did not manufacture this ammunition in enough quantities to meet the market demands. The rifle also had mechanical issues and was affected by dust as well. These were some of the reasons why it was not to be accepted by the US Army in 1872. The company tried to enter the commercial market, but the lack of availability of ammunition for it caused it to not sell well. Also, after the Civil War (1861-1865), there was a surplus of firearms available on the market for cheap and the company could not compete on price against older established firearms companies. By 1879, the company went bankrupt and its assets were sold by March 1881.


Sunday, June 29, 2014

Helical Magazines

In our last article, we studied the rotary magazine. In today's article, we will study a magazine that was invented more recently. Today's object of study will be the helical magazine.

The helical magazine was invented by Michael Miller and Warren Stockton in 1985 and produced by the California Instrumentation Company (later known as "Calico"). Interestingly, the California Instrumentation Company was originally known for manufacturing specialized instrumentation for the petroleum industry, but since they already had experience in tooling and engineering, they didn't have too much trouble manufacturing firearms. By about 1988 or 1989, they had the bugs ironed out and started producing them in quantity, along with firearms designed to use these magazines.

Image from the patent application for the helical magazine. Click on the image to enlarge. Public domain image.

The concept behind the helical magazine is to arrange the cartridges in a helical spiral, as shown by figure 2 above. A drive spring rotates the drive member and pushes the cartridges into the chamber. The figure below shows a cutaway of how the magazine works:

Cutaway of a helical magazine on a Calico firearm. Click on the image to enlarge.

The full patent details for this type of magazine may be viewed here. The nice feature of this type of magazine is that it can hold a lot of cartridges in a pretty compact space.


Unfortunately for Calico, the Federal Assault Weapons ban came into effect in 1994 (and was in effect until 2004). This law stated that no firearms manufacturer could produce magazines with greater than 10 cartridge capacity. Therefore, Calico could not really sell their firearms during this period because their biggest selling point was that the magazine could hold a lot of cartridges. Only after 2004 when the law was changed, could they restart manufacturing their firearms. Calico now offers firearms that have 50 and 100 cartridge capacities.

The idea of a helical magazine was copied by other countries, most notably by Russia, China, Hungary, North Korea etc.. The Russian Bizon submachine gun is one such weapon that uses this concept.

Bizon submachine gun. Click on the image to enlarge.
Image is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license by Vitaly Kuzmin

The above image is a Russian Bizon submachine gun. The word Bizon is the Russian word for "Bison". The long cylindrical tube that you see under the barrel in the image above is the helical magazine. It comes in two versions: one is chambered for the 9x18 mm. Makarov cartridge and the other model uses the popular 9x19 mm. Parabellum cartridge. Magazine capacity is 64 cartridges for the Makarov cartridge and 53 cartridges for the Parabellum cartridge. Incidentally, two of the designers of this firearm have very famous parents as well: Viktor Kalashnikov (son of Mikhail Kalashnikov, designer of the AK-47) and Alexi Dragunov (son of Evgeny Dragunov, inventor of the SVD sniper rifle).

Compared to box magazines (which can hold about 30-40 magazines before becoming unwieldy), helical magazines can hold a lot more cartridges in a relatively compact space. However, unlike drum magazines, a helical magazine does not stick out of a firearm so much as to affect the balance and ergonomics. On the other hand, helical magazines have a lot more parts than other magazine types (as you can see by the image of the magazine sub-assembly above), so disassembling one can be complicated. Also, loading and unloading the magazine must be done one round at a time, which means it can take a while to do this.


Monday, June 23, 2014

Rotary Magazines

A few posts ago, in our study about capsule magazines, reader William Reichlinger posted an interesting comment asking whether a 1941 Johnson rifle uses a capsule magazine or not and that wikipedia mentions that it is a rotary magazine and whether it is a subclassification of a capsule magazine or not. Therefore, in today's post, we will study all about the rotary magazine.

To answer the question briefly, a rotary magazine uses a different feed mechanism than a capsule magazine. A capsule magazine has a spring and follower to push rounds from the magazine into the chamber and it is always a fixed magazine. A rotary magazine, on the other hand, can be either a fixed or detachable magazine and the feeding mechanism consists of a sprocket (or sprockets) that is rotated by a torsion spring. The cartridges fit between the teeth of the sprocket and as the sprocket rotates, it feeds the rounds to the chamber. The figure below shows the various parts and the completed assembly of a rotary magazine.

Parts of a rotary magazine. Click on the image to enlarge.

The cartridges fit between the teeth of the two sprocket wheels and are fed into the chamber of the firearm, powered by the tension of the torsion spring.

One of the early designs for a rotary magazine design is by Otto Schonauer in 1885. Otto Schonauer was a protege of the famous German firearms designer, Ferdinand Mannlicher and his rotary magazine design appeared in a turnbolt Mannlicher .43 caliber rifle design in 1887. However this rifle was not very successful and the magazine was not perfected yet. A much improved rotary magazine was featured in the Mannlicher-Schonauer M1903 rifle design, which was very successful.

Diagram of a Mannlicher rotary magazine by itself. Click on the image to enlarge
 A Mannlicher rotary magazine attached to a rifle. Click on the image to enlarge.

Meanwhile, over in the United States, Arthur Savage was also working on a rotary magazine design, which he perfected in 1893 and obtained a patent for it. This design was used in the Savage M1895 and Model 99 rifles.

Patent documentation for the Savage Model 99 rotary magazine. Click on the image to enlarge. Public domain image.

Interestingly, this rifle's rotary magazine design also includes a counter that shows the user how many cartridges are left in the magazine. It must be noted that not all Savage Model 99 rifles have this rotary magazine, as some later versions feature a box magazine instead. The Model 99 was produced by Savage for nearly 100 years (1899 - 1998) and has been chambered for many different cartridges.

Another firearm that uses a rotary magazine is the Johnson M1941 rifle, which we mentioned at the start of this post. This rifle was invented by Melvin Johnson and the magazine design is shown below from his patent application:


Click on the images to enlarge. Public domain images.

The entire Johnson patent document may be viewed online here.

Some other firearms that use this sort of magazine include the hugely popular Ruger 10/22 rifle and the Steyr SSG 69 rifle.

A rotary magazine used by a Ruger 10/22 rifle. Click on the image to enlarge. Public domain image.

The above image shows a rotary magazine used by a Ruger 10/22 rifle. This particular model holds 10 cartridges and is made of clear polycarbonate plastic and allows the user to see how many cartridges are left in the magazine. Many American readers of this blog will recognize this type of magazine because this is what comes with the standard model of the Ruger 10/22 rifle. For non-American readers, the Ruger 10/22 is one of the most popular rifle models in the US since 1964, because of its affordable price, ability to be customized, widespread availability of third party components and low cost of ammunition, and it is often the first rifle for many Americans.

Rotary magazines typically have a capacity of around 5 to 10 cartridges, which means they don't hold as many cartridges as some of the other magazine types we studied earlier. On the other hand, many rotary magazine designs fit right into the magazine's stock, without protruding out like a box magazine or a drum magazine do, which makes them much more convenient. In some rifles, the rotary magazine fits right where the center of gravity of the rifle is. Rotary magazines can also use spitzer type pointed bullets safely. In fact, the Savage Model 1895 was one of the first lever-action rifles to use spitzer bullets, as previous lever-action rifles used tubular magazines, which as we saw earlier, are not safe to use with centerfire cartridges using spitzer bullets.

Monday, June 16, 2014

Pan Magazines

In our last post, we studied the drum magazine. In today's post, we will study another type that looks very much like the drum magazine, but operates a bit differently. Today's object of study will be the pan magazine.

The pan magazine is a flat cylindrical shape, similar in shape to a drum magazine. However, if you look at the previous post, drum magazines are mounted from below the gun. A pan magazine, on the other hand, is mounted on top of the gun and uses the force of gravity to drop cartridges into the action. One more difference is that the cartridges in a pan magazine are arranged perpendicular to the axis of rotation, whereas the cartridges in a drum magazine are arranged parallel to the axis of rotation. The easiest way to understand it is via some pictures.

A pan magazine from a Lewis gun. Click on the image to enlarge.

As you can see from the above image, the cartridges are arranged like the spokes of a wheel in a pan magazine. Compare this to how the cartridges are arranged in a drum magazine, as seen in our previous post.

One of the first firearms to feature a pan magazine, was the Bira gun, which we studied many months ago.

A Bira Gun. Click on the image to enlarge.

The flat circular object that you see on top of the gun is the pan magazine. In the Bira gun, this magazine is designed to hold .577-450 Martini cartridges in two layers of 60 cartridges each, giving the magazine a capacity of 120 cartridges. As the crank (which can be seen on the side at the rear of the gun) is turned, the magazine is rotated via a ratchet mechanism. There is a stationary plate at the bottom of the pan, which has a slot in it, big enough for a cartridge to fall through into the action.

Another gun that features a pan magazine was invented in 1898 by Howard Carr, a well-known shooter (he once held a world-record for pistol shooting), and manufactured by the San Francisco Arms Company. The details of his patent may be viewed here.

Image from Howard Carr's machine gun patent claim. Public domain image. Click on the image to enlarge.

In the above drawing, note how the cartridges sit on top of each other in the magazine. This allows the magazine to hold a large number of cartridges.

Some other guns that feature pan magazines are the Lewis gun, the Bren light machine gun, the Degtyarev light machine gun and the American-180 submachine gun. 

A Lewis gun. Click on the image to enlarge. Public domain image.

A Degtyarev gun. Click on the image to enlarge. Image copyright Polish Ministry of National Defense and used with permission.

In the case of the Bira gun and the Lewis gun, the pan magazine has notches or teeth on the outside of the magazine cover, which can be driven by a ratchet and pawl mechanism. In the case of a Bren gun or an American-180, the magazine is rotated by unwinding a circular spring.

Like drum magazines, pan magazines can hold a pretty large number of cartridges. The Bira gun's capacity is 120 cartridges, the Howard Carr machine gun magazine holds 310 cartridges, the Bren magazine holds 100 cartridges, the Lewis gun holds 47 or 97 cartridges, the Degtyarev holds 47 or 60 cartridges and the American-180 can hold 165, 177, 220 or 275 cartridges, depending on the model of magazine. Since a pan magazine sits flat on top of the gun, this means the gun doesn't take up too much vertical height and this allows the soldier to lie prone on the ground without exposing himself much.