Heavy Machine Guns - I

In our last post, we looked at light machine guns. In today's post, we will look at another class of machine guns, the Heavy Machine Gun (often abbreviated as HMG).

In the late 1800s, there arose a need for a firearm that could fire in automatic mode, with good accuracy over longer ranges, for a long amount of time. Such a weapon could be used by a small group of soldiers in a key position to defend against a much larger group of enemies armed with inferior weapons and prevent them from advancing. Unlike light machine guns, these weapons needed to fire in automatic mode for much longer periods. This led to the development of heavy machine guns, weapons that can literally lay down huge volumes of fire, for very long periods of time.

The first heavy machine gun in history was the Maxim gun, invented in 1884 by Sir Hiram Maxim, an American inventor settled in England (he later became a British citizen in 1900). He was a prolific inventor and invented several items including a curling iron, several gas and steam engines, electric light bulbs, automatic sprinklers, motor cars etc. In 1882, he was in Vienna and ran into another fellow American that he knew from his time living in America, who informed him that "Hang your chemistry and electricity! If you want to make a pile of money, invent something that will enable these Europeans to cut each others' throats with greater facility." As a child, Sir Maxim had fired a large gun and had been knocked down by the recoil. This incident inspired him to invent a recoil operated machine gun (he also patented gas operated and blowback systems between 1883 and 1885). While he was inventing his gun, he announced in the local papers that he was experimenting with a new type of gun in his garden and advised his neighbors to keep their windows closed, in order to avoid getting injured by broken glass!

Maxim's first prototype weighed around 26 pounds (11.8 kg.), but was not capable of firing for long periods of time because of overheating problems. To solve this issue, he put a water jacket around his barrel. He also increased the caliber to fit a .303 British rifle cartridge. This made his rifle design heavier and it weighed around 60 pounds (27.2 kg.)

A Maxim machine gun. Click on the image to enlarge.

Image licensed under the Creative Commons Attribution-Share Alike 3.0 License by Jonathan Cardy at Wikipedia

Such a heavy gun required a team of people to operate: one man to fire the weapon and the others to reload ammunition, refill water, spot targets, help carry the gun and ammunition from one position to another etc. While Maxim tried to sell his invention to various European countries, many of them were suspicious about machine guns in general, because of jamming issues on previous models. Luckily for Maxim, the British had appointed Sir Garnet Wolseley as commander-in-chief in 1888 and he was a big believer in new technologies and placed an order for 120 Maxim machine guns in October, using the same .577/450 cartridges of the Martini-Henry rifle. The Maxim guns proved their worth in 1893/1894, in the First Matabele War in Africa., where a small unit of British soldiers armed with just four Maxim guns held off a force of 3500-5000 African Ndebele warriors. After this and several other encounters, other governments started to take notice and placed orders for heavy machine guns as well.

Early Maxim guns had a problem of heavy smoke obstructing the view of the gunner very quickly, but the invention of smokeless powders solved this issue. Incidentally, Hiram Maxim himself was one of the pioneers of smokeless powders and he and his brother, Hudson Maxim, were granted a patent for a particular type of smokeless powder. However, the patent was issued in the name of "H. Maxim" and his brother took advantage of this to stake a claim for the patent and later moved back to the United States, where he developed several more explosives and sold the rights to the DuPont Chemical Company. Because of this patent dispute, Hiram Maxim stayed in Europe, while his brother moved back to the United States and the brothers never spoke to each other ever again.

Due to years of experimenting with loud guns, Sir Hiram Maxim's hearing was damaged and he began to go deaf later in life. In a twist of fate, a device that could have saved his hearing, the Maxim silencer (suppressor), was invented by his son, Hiram Percy Maxim in 1908.

In our next post, we will look into further developments of heavy machine guns.

Actions: Recoil Action: Short Recoil Operation

In our previous post, we studied the basics of recoil operated actions. In this particular post, we will study one of the types of recoil operated actions, i.e. the short recoil operation.

This action type has a long history, being the action that was used in the first machine gun ever invented, i.e. the Maxim machine gun. It is also the action of choice for most semi-automatic and automatic pixels that use 9 mm. Luger (9x19 mm.) cartridges or bigger. Smaller and lower powered cartridges are used with blowback actions that we studied last month, but once the cartridges get beyond a certain size and power, a blowback action cannot be used any more and most modern pistols therefore use a short recoil operation.

As we noted in our previous post, one of the key differences between a blowback action and a recoil operated action is that a recoil operated action has the bolt (i.e. the metal block that holds the cartridge in the chamber before firing) is locked at the point of firing, whereas a blowback action merely has it held under spring pressure. This enables the recoil operated action to fire heavier cartridges. Also, as we noted previously, in a recoil operated action, some parts of the weapon are allowed to recoil backwards, whereas other parts are held stationary relative to the recoiling parts. In a short recoil action, the parts that are allowed to recoil are the barrel and the bolt.

At the point when the bullet is fired, the barrel and the bolt are locked together and move backwards due to recoil. After a short distance of travel (a few mm. in the case of pistols and a few caliber lengths in the case of machine guns), the bolt and the barrel disengage from each other. How this is achieved is what differentiates various short recoil operation systems. In some cases, the barrel is slowed down, in other cases, the bolt is accelerated. In either case, the barrel stops moving, whereas the bolt continues to move backwards and compresses a recoil spring and also extracts the old cartridge case at the same time, which is ejected via a side port. The recoil spring then pushes the bolt forwards and as the bolt moves forwards, it picks up the new cartridge from the magazine and pushes it and the barrel forwards. When the barrel reaches its forward position again, the bolt and barrel lock again and the weapon is ready to be fired.

As was mentioned above, in some systems, the barrel is slowed down to separate the barrel from the bolt. Weapons that use this include the classic Colt M1911 pistol designed by John Browning, all Glock pistols, Smith & Wesson, FN Browning, SIG Sauer etc.

In the case of the Browning designed Colt M1911, the bolt, barrel and slide all move backwards together initially, but then a barrel link tilts the barrel downwards. As the barrel tilts, the barrel locking lugs unlock themselves from the slide recesses. The bolt and slide continue to move backwards and an extraction claw on the slide also pulls the spent cartridge out of the chamber.

An ejector strikes the back of the spent cartridge and pushes it out of the extraction port, as the slide and bolt continue to move backwards. When the slide and bolt reach the back of the pistol, the recoil spring pushes them forward and during the forward motion, the slide locks back into the barrel and the three pieces then move back together. The two animated movies below show how this works.

In the case of Glock, SIG Sauer and most recently designed automatic pistols, this mechanism is even more simplified. There is a downward inclined ramp attached to the back of the barrel. As the barrel and slide move backwards, the ramp contacts a fixed stud on the pistol's frame. This causes the back of the barrel to move down (and the front to tilt up), which moves it out of engagement with the slide. The rest of the action is similar to what was described earlier. The animation below shows exactly how this works:

In the above three animations, the one thing is common is that the bolt and barrel initially move backward together and are then separated by slowing down the barrel while leaving the bolt and slide free to continue moving backwards.

Another way to achieve this separation is by accelerating the bolt after they both move back together. This mechanism is most commonly used today in the 7.62 mm. and 12.7 mm. M2 machine guns invented by (surprise, surprise) John Browning! The 12.7 mm. M2 is still used in the famous Abrams tank, as well as most other western tanks, which shows the reliability and timelessness of this design. In the M2 machine gun, the barrel and bolt initially recoil together about 10 mm. backwards and then a rotating cam in the receiver disconnects the bolt from the barrel. The barrel has an extension in the back and bottom of the barrel. After the bolt and barrel are disconnected, this extension then strikes a short, curved lever. The lever is pivoted so that it has a mechanical advantage and therefore it pushes and accelerates the bolt rearward. A fixed stud stops the barrel extension, which also halts the barrel, while the bolt continues rearward. As before, we have an animation to show how it works:

We will continue studying short recoil operations tomorrow, where we will deal with some more historical short-recoil operated weapons such as toggle-bolt short recoil actions. It'll be interesting reading!