Tuesday, August 19, 2014

Medium Machine Guns - I

In our last few posts, we looked at light machine guns and heavy machine guns. Briefly, a light machine gun fires intermediate-sized ammunition, comes with a bipod, operated by a single user and is generally carried by and used to support infantry. A heavy machine gun fires larger-than-ordinary rifle cartridges, is mounted on a vehicle or a tripod, sometimes operated by a team of people and is used against troops, light armor, buildings, low flying aircraft etc. In today's post, we will study another class of machine guns, the medium machine gun, otherwise called the MMG.

A medium machine gun is a weapon that fires full-sized rifle cartridges in automatic mode. They are generally air-cooled and belt fed. They also weigh somewhere in between the weight of a light machine gun and a heavy machine gun. Typical weight for a MMG is somewhere between 25 lbs. and 40 lbs. (or 11.34 kg. to 18.14 kg.) They began to emerge towards the end of World War I, as a balance between light machine guns and heavy machine guns. Recall that in World War I, light machine guns were made to be fed by smaller box magazines and fired in bursts only. Medium machine guns were designed to be fired on automatic for much longer, but without the heavy water cooling mechanism, weight or recoil of a heavy machine gun. Therefore, a medium machine gun offered flexibility to be used with a bipod by infantry like a light machine gun, or mounted on a heavier tripod or vehicle and used similar to a heavy machine gun. For this reason, a medium machine gun is sometimes referred to as "General Purpose Machine Gun (GPMG)" or "Universal Machine Gun".

The first real MMG was the Browning designed M1919 medium machine gun. This is a weapon that fires .30 caliber rifle cartridges from an ammunition belt. It was designed as an air-cooled variant of the M1917 heavy machine gun. Unlike the M1917 which weighs 103 lb. (47 kg.), the M1919 only weighs 31 lbs. (14 kg.) The minimum number of people needed to operate it is two, but sometimes upto four people were involved: a gunner (who fired the gun and also carried the tripod and some ammunition, when moving the gun), an assistant gunner (who fed the ammunition and carried the gun, when on the move) and two other people to carry extra ammunition, barrels, tools etc.

US Marines operating a M1919 A4 during World War II. Click on the image to enlarge. Public domain image.

This weapon was heavily used in World War II by different branches of the US military. It was used by infantry troops, mounted on jeeps, tanks, armored personnel carriers, aircraft etc. and continued to be used well into the Vietnam era. It was also used by other military forces around the world and modified to take other rifle cartridge calibers as well, such as .30-06, 7.62x51 NATO, .303 British, 7.62x54 mmR etc. In fact, it is still in use in some parts of the world.

In our next post, we will look at some more medium machine guns.

Sunday, August 17, 2014

Heavy Machine Guns - III: Modern HMGs

In our last couple of posts about heavy machine guns, we saw that they were weapons designed to fire rifle cartridges for long periods of time. Since they were designed for firing in automatic mode for hours, the designs were bulky and the early machine guns were water-cooled, which contributed even more to the weight. Therefore, these weapons needed multiple people to operate effectively and inconvenient to move around and were mainly used as defensive weapons. Heavy machine guns of this type were used extensively in the trench warfare conditions of World War I, against enemy infantry.

World War I also saw the introduction of armored vehicles, such as the British Mark-I tank and the German Junkers J.I airplane. Against such armor, ordinary infantry rifle ammunition (like the .30-06) was useless. Therefore, there was a need for a weapon that could defeat lightly armored vehicles, buildings, aircraft etc. and could do so at longer ranges. In 1917, General Pershing posted a request back to the US Army Ordnance Department, asking for a rifle to be designed, that could fire a bullet of at least .50 inches (12.7 mm.) diameter at a velocity greater than 2700 feet/second (820 meters/second). The famed designer, John Browning, went to work on this request. He took his earlier .30 caliber machine gun model and scaled it up to fire a .50 BMG (12.7x99 mm.) caliber cartridge. His initial design used water cooling, just like other heavy machine guns of that era. The design came too late to be used in World War I, but was accepted later by the US Army and Navy as the M1921 (curiously though, despite the name, it actually went into production in 1929!).

After Mr. Browning passed away in 1926, further development work on this gun went on, led by Dr. S.H. Green. By studying the needs of the US Army, Navy and Air Force, Dr. Green realized that a single machine gun model could not accommodate everyone's requirements. Hence, he redesigned the M1921 to a model that could be changed into seven different .50 caliber machine guns, all using a common receiver component, but switching the other components such as the barrel, water jacket etc. The new model machine gun was called the M2 heavy machine gun and was manufactured in its different versions by Colt, starting in 1933. One of the versions did not have a water jacket, but instead had a heavier air cooled barrel, which was designed to be quickly changed. The lack of the water jacket meant that the barrel had to have a larger surface area and have more mass to compensate, therefore this variant was called the M2 HB (HB standing for "Heavy Barrel"). However, this version was lighter compared to the water-cooled versions: the water-cooled M2 versions weigh about 121 lbs (55 kg.) and the air-cooled M2 HB only weighs 84 lbs (38 kg.) in comparison. Another even lighter version, with a thinner barrel designed exclusively for aircraft use, only weighs 60 lbs (27 kg.) and was used by many US aircraft in World War II.

It must be noted that World War II changed the nature of warfare in several ways. The German Blitzkrieg strategies showed the effectiveness of maneuver warfare and static machine gun positions that were so effective until World War I, became obsolete and useless. In this environment, a lighter heavy machine gun model that can be moved around relatively easily, is much more useful than a heavier water cooled model.

M2 Heavy Machine Gun on a M3 tripod. Public domain image.

While the M2 HB weighs 84 lbs. (38 kg.), it must be noted that the M3 tripod stand that it is mounted on weighs an additional 44 lbs. (20 kg.). The gun is also designed to be mounted on jeeps, armored vehicles, ships or anti-aircraft turrets. It can fire a variety of rounds, ranging from standard ball ammunition to armor piercing, incendiary etc. This weapon was very successfully used by various branches of the US military in World War II and continues to be used by the US military to this day. It is also used by military forces of many other countries in the world. It exemplifies the modern definition of the heavy machine gun, as we know it today.

To summarize, the early heavy machine guns were designed to use standard rifle ammunition, were water cooled and bulky, capable of long range firing, and designed to be used in static defensive roles. The modern definition of a heavy machine gun is a weapon that is designed to use much larger ammunition calibers, is air-cooled, has quick change barrels to solve overheating issues, is less bulky than water-cooled models, capable of long range firing, is designed to be moved around relatively easily, and can be used in both defensive and offensive roles. Modern heavy machine guns are designed to be used, not only by infantry, but also by jeeps, tanks, humvees, boats, ships, aircraft etc.

A M2 HMG in a firebase overlooking the Korengal valley in Afghanistan. Click on the image to enlarge. Public domain image.

US Marine from the 24th Marine Expeditionary Unit with a vehicle mounted M2 heavy machine gun. 
Click on the image to enlarge. Public domain image.

Modern heavy machine guns include the above mentioned M2, the Soviet DShK 1938 (another World War II era design), the Russian Kord HMG etc.

Tuesday, August 12, 2014

Heavy Machine Guns - II

In our last post, we looked at the early developments in heavy machine guns and the work done by Hiram Maxim. We will continue our studies on this topic today.

When we last left off, Hiram Maxim had invented the Maxim gun and had founded a company in England to manufacture them. What was not mentioned in the previous post was that he took on a partner for funding the new Maxim Gun Company. This partner was Albert Vickers, son of Edward Vickers, who was one of the founders of a prosperous steel foundry business and also had interests in manufacturing armor plating and shipbuilding. In 1896, the parent Vickers company bought out the Maxim Gun Company and got into the machine gun manufacturing business as well. Vickers took the basic Maxim gun design and simplified the firing mechanism and also used more modern alloys in the construction, thereby reducing its weight slightly. The Vickers machine gun was formally adopted by the British army in 1912 and was used pretty heavily in World War I, both by the army and the airforce (it was fitted into several British and French fighter aircraft).

Vickers machine gun in action during World War I. Click on the image to enlarge. Public domain image.

Like its predecessor, the Maxim machine gun, the Vickers also has a barrel surrounded by a water jacket, in order to cool down the barrel. Upon firing the barrel rapidly, the water would turn into steam and exit out via a port at the muzzle end, into a separate steam chest. Here, it would condense back into water. This system has the advantage that the rising steam does not give away the gunner's position and the water can be reused. It was recorded that if the water ran out, crews were known to pee into the water jacket.

In British use with the .303 cartridge, this weapon has a range of over 4000 meters. The gun weighs about 30 lbs (13.6 kg.) by itself, without any ammunition or water. With a full load of water (about 4 liters) in the water jacket, it weighs about 40 lbs (18 kg.). Then, there is the tripod stand, which weighs about 50 pounds (23 kg.) and the ammunition boxes, which contain 250 cartridges held in a cloth ammunition belt and weigh about 22 lbs (10 kg.) each. In addition to this, the weapon also comes with spare barrels, steam chest, pipes etc. With all this weight, the gun needed about six to eight people in a crew to operate it: one to fire the gun, another to assist with feeding the ammunition and reloading it and the rest to carry the weapon, extra ammunition and spare barrels. If the gun needed to be moved, the crew would disassemble it into lighter component parts, while one of them stood guard with an ordinary rifle.

The gun was designed to fire 10,000 rounds per hour, after which the barrel would have to be replaced by a new one. With a trained crew, this barrel replacement operation only took a couple of minutes to accomplish. Therefore, the gun could be used to fire almost continuously for very long periods of time. In August 1916, the British Army's 100th Company of the Machine Gun Corps fired their ten Vickers guns continuously in battle for about 12 hours straight. During this time. they interchanged about 100 barrels and it is recorded that they fired over 1 million cartridges without a single failure!

It was during World War I that the classification between heavy machine guns and light machine guns started. Light machine guns like the Lewis gun were issued to normal infantry units. Heavy machine guns like the Vickers were issued to new units called Machine Gun Corps.

As the reader can probably see, the differences between the light and heavy machine gun classifications now become clear. Light machine guns are lighter, come with bipods and are designed to fire short bursts of ammunition, whereas heavy machine guns are much heavier, are mounted on tripods or vehicles and can fire on automatic for much longer periods. Light machine guns are issued to advancing infantry units to support an attack, whereas heavy machine guns are more geared towards staying at a fixed position and defending against advancing infantry or cavalry.

The Vickers gun was known for reliability and was sold to several countries in a variety of calibers. It was in service with various countries from about 1912 to 1968. Unlike the light machine guns that we studied before, this gun is capable of firing almost continuously, literally for hours.

In our next post, we will look at the modern definition of heavy machine guns.

Monday, August 11, 2014

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.

Sunday, August 10, 2014

Light Machine Guns

In our discussion about general features of machine guns, we discussed different classes of machine guns. Today, we will study the first of those classes, the light machine gun (often abbreviated as LMG).

Light machine guns were originally developed to support infantry squads, by providing short bursts of suppressive fire, designed to keep the enemy's heads down and allow friendly soldiers to advance. The first light machine guns were developed around World War I. Early machine gun examples include the Browning BAR M1918, Lewis gun, Madsen machine gun etc. In present day military forces, many infantry units carry one LMG per fire team or squad.

Browning Automatic Rifle (BAR) M1918, designed during World War I. Click on the image to enlarge. Public domain image.

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

The word "light" is a bit of a misnomer, because most LMGs are heavier than the assault rifles that the rest of the team carries. However, they are lighter than the other classes of machine guns that we are going to study in the following posts.

Light machine guns are generally designed to use the same ammunition as the rifles carried by the rest of the unit. This feature allows the different soldiers to share ammunition during a battle. For instance, the Browning M1918 uses .30-06 ammunition, the same as the M1903 rifle carried by US soldiers in World War I, the M249 SAW uses the same 5.56x45 mm. ammunition used by M16 rifles etc. Since LMGs are designed for automatic fire, many feature high capacity magazines, such as drum magazines, pan magazines or ammunition belts. However, some models of LMGs are designed to use the same box magazines as the assault rifles carried by the rest of the unit, so that they can share both magazines and ammunition between themselves. Some newer LMGs are designed to use multiple methods of feeding ammunition. For instance, the FN Minimi, the M249 SAW, IMI Negev and the Heckler & Koch MG 43 (now known as the MG4) are designed to use both ammunition belts, as well as box magazines. This allows the machine gunner maximum flexibility in using ammunition and magazines during a battle.

A M249 equipped with an ammunition belt. Click on the image to enlarge. Public domain image.


While the LMG is light enough to be carried by a single soldier and fired from the hip, it is generally fired from the prone position. Because of this, many LMGs have a bipod attached to the front of the barrel, to allow the user to comfortably operate the weapon from the prone position.

In recent times, many LMGs are modifications of an existing assault rifle design. Examples of these include: RPK (Russian LMG design based on the AK-47), Steyr AUG LMG (Austrian rifle based on the Steyr AUG rifle family), INSAS LMG (Indian rifle based on the INSAS rifle family) etc. However, the LMG versions are generally designed with longer and heavier barrels, to sustain automatic fire for longer periods of time without overheating. Some models (such as the Steyr AUG LMG) have quick change barrels to solve the overheating problem. The parts of the action are also designed to be more robust than the assault rifle versions, in order to shoot in full automatic mode for longer periods of time.


An INSAS Light Machine Gun. Click on the image to enlarge.

A Bren gun. Public domain image.

The above image shows a Bren gun Mark I. Note the curved box magazine mounted on top of the rifle and the carrying handle in the middle of the gun, which also doubles as a tool to remove a hot barrel. Later models came with heavier chrome-lined barrels, which reduced the need to interchange barrels. The Bren gun was first adopted in 1938 by the British, produced by various commonwealth countries (UK, Australia, Canada, India) over the years and is still being manufactured currently in India!

The Madsen machine gun also has a long history, being originally manufactured by Denmark in 1902 and still going strong in the hands of Brazilian military police, well into the 21st century! It just goes to show that good designs can last a really long time.,

In our next post, we will study another class of machine guns: the heavy machine gun.


Saturday, August 2, 2014

Early Machine Guns

In our last post, we looked at some basics about machine guns. In today's post, we will study some early developments in machine gun history and what technologies needed to be invented along with them.

One of the early developments in weapons capable of firing multiple shots before reloading was the Puckle gun, which we already studied some time ago. This was invented in 1718 and is the precursor of the revolver.
A Puckle gun. Click on the image to enlarge. Public domain image.

There were also other multi-shot weapons invented later, such as the Mitrailleuse gun and the Belton flintlock, but the first real practical machine gun was the Gatling gun, invented by Richard Gatling in 1861.


In order to have a rapid firing weapon, it was necessary to have a way to automate/quicken the reloading process and the invention of the cartridge came in handy here. Early gatling gun models used paper cartridges and percussion caps, because these were the same technologies used by US Army infantrymen of that era -- in fact, the Gatling gun was designed to use the same caliber cartridges. However, this model was prone to jamming. The second model used the rimfire cartridge instead. Rimfire and centerfire cartridges made the Gatling more reliable. Metallic cartridges also made it possible to provide a better seal in the chamber of the firearm, because the hot gases from a fired cartridge expands the metal case and seals the back of the chamber.

Another technology that made it possible for modern machine guns was the invention of smokeless powder. Early Gatling guns used black powder cartridges. With black powder, the smoke rapidly makes it hard for the operators to see what is going on. On top of that, black powder leaves behind a lot of dirty residue and this can cause the mechanism of a machine gun to jam. Smokeless powders produce a lot less residue, therefore the gun can fire for longer periods without risk of jamming.

Improvements in metallurgical techniques also helped, because it made it possible to make gun parts which perform reliably for extended periods of time and resist heat better as well.

With that said, heat dissipation has always been a problem in machine gun design. In the case of the Gatling gun, the problem was solved by using multiple barrels. With multiple barrels, the weapon can fire at a higher rate, but each barrel is rotated after each shot and therefore has time to cool before it fires another shot. However, the presence of multiple barrels makes the overall weapon heavier. Water cooling and quick-change barrels are other techniques that were historically used by other machine guns to solve the same issue. Interestingly, the use of multiple barrels in a gun was revisited in modern times, with the invention of the minigun and the multi-shot cannon used on the A-10 Warthog aircraft.

Also, the idea of using an electric motor to power a gun is a lot older that most people realize. In fact, in 1893, Richard Gatling received a patent for a gatling gun powered by an electric motor!


Wednesday, July 30, 2014

Machine Guns - General

In our last few posts, we studied different feed systems such as ammunition belts, chain feeds and feed strips. All these mechanisms are generally used with machine guns. Therefore, in the next series of posts, we will study all about machine guns.

A machine gun is a firearm that is capable of fully automatic fire. What this means is that as long as the firearm has ammunition available to it and the trigger is pulled, it will continue to load and fire ammunition automatically. Machine guns are capable of firing at high rates of several hundred rounds per minute and are designed to keep firing for considerable periods of time. The capability of maintaining sustained fire for long periods of time is what distinguishes a machine gun from an automatic rifle or an assault rifle (both of which can fire on full-auto only for limited periods of time).

US military doctrine has another interesting way of classifying automatic rifles versus machine guns. If the fully automatic firearm is operated by a crew, then it is a machine gun, but if a fully automatic firearm is operated by a single person, then it is an automatic rifle. In many cases, weapons fall exclusively into one of these two designations, however, we have one major oddball that falls into both categories -- the M249. US Army Field Manual FM 3-22.68 ("Crew-Served Machine Guns") describes the M249 as both an automatic rifle and a machine gun! Quoting from the manual chapter 4, section 5, paragraph 4-207, "Both the M249 automatic rifle and the M249 machine gun are identical, but its employment is different. The M249 automatic rifle is operated by an automatic rifleman, but its ammunition may be carried by other Soldiers within the squad or unit. The M249 machine gun is a crew-served weapon."

Machine guns can be portable as well as mounted and therefore, they are generally classified based upon size.

Before we dig deep into the topic, let us talk about submachine guns, which are portable firearms that are designed to fire pistol-sized ammunition. While they have a high rate of fire, some authorities do not consider these as "true machine guns" as they are not capable of sustained fire for long periods of time. Examples of these would be the Thompson submachine gun (which actually coined the term "submachine gun") also known as the Tommy gun, Chicago typewriter, Trench broom etc., Heckler & Koch MP5, Uzi etc. All these weapons are designed to fire pistol sized ammunition such as .45 ACP, 9 mm Parabellum etc.

Next, we have true machine guns like the Light machine gun, Medium machine gun, Heavy machine gun, General purpose machine gun which all use larger ammunition calibers (rifle calibers or larger). These weapons are generally heavier than other automatic weapons (even the "light" machine gun is heavier than an assault rifle, for instance). Examples of these would be the Lewis gun, the Bren gun, MG-34, Browning M1917, Browning M2, M60 etc.

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

A M60 machine gun. Click on the image to enlarge. Public domain image.

We will study more into these various types of machine guns in the following posts.

Finally, we have weapons in the autocannon category. The difference between an autocannon and a machine gun has largely to do with the type and size of ammunition. If the firearm uses ammunition greater than 16 mm. diameter, or if it uses large caliber explosive rounds, then it is considered an autocannon rather than a machine gun. Examples of an autocannons include the M242 Bushmaster (which we studied briefly, when recently studying about chain guns), Oerlikon 20 mm. autocannon etc.

Since machine guns are designed to fire on automatic for longer periods of time, they tend to overheat quickly. Hence, many of them are either designed to have a built in barrel cooling system or feature a quick-change barrel replacement system. For the same reason, most machine guns are also designed to fire from an open-bolt, so that the breech area can be more efficiently air-cooled when the gun is not firing.

In the next few posts, we will study all about various types of machine guns and their history.