For over a century, machine guns have had a major effect on ground combat. Their efficacy against infantry prompted the invention of the tank in World War I, for instance. They've changed the way wars are fought and have played a huge role in forging history.
That said, it's important to keep in mind that not all machine guns are the same, and getting the nomenclature right is important. While this isn't as hotly contested as the debate between "magazine" and "clip", it can get touchy. We're talking about some cool machine guns here, we want to make sure we're using the right terms as we imagine letting loose on a range with them.
There are several types of machine guns. Let's take a look:
Original HMG – Heavy Machine Guns
As originally understood, this term applies to water-cooled guns intended to provide a sustained volume of fire, like Germany's Maxim machine guns that were used in World War I or the Browning M1917. HMGs are typically heavy, stationary weapons. They might not be very mobile, but as a grunt, you don't wanna have to charge them.
United States Army personnel, including the son of John Moses Browning, fire an M1917 heavy machine gun. (U.S. Army photo)
MMG – Medium Machine Guns
These guns emerged in World War II as a more mobile option for sustained fire. The M1919A4 is a prime example. MMGs don't provide as much sustained fire as water-cooled guns, but their versatility and firepower have proved to be very lethal.
Marine Pfc. Douglas Lightheart cradles his M1919 30-cal. machinegun as he and his buddy, Pfc. Gerald Churchby, take time out for a cigarette while fighting on Peleliu Island. (U.S. Marine Corps photo by Cpl. H. H. Clements)
AR – Automatic Rifle
The automatic rifle emerged in World War I. The earliest issued rifles, namely the French Chauchat, were pieces of crap, but later offerings, like the Browning Automatic Rifle, were mainstays of World War II. Today, the Marines field the M27.
A U.S. Marine fires the Browning Automatic Rifle in World War II. (Photo: U.S. Archives)
LMG – Light Machine Gun
The light machine gun was another strike at finding that sweet spot between firepower and mobility. Like an automatic rifle, it uses a box magazine and you can fire it from your shoulder. However, using the bipod is highly recommended for accuracy. When you think LMG, think Bren or Lewis.
British troops take a rest, with a Bren light machine gun visible on the trail. (Photo from Imperial War Museum)
GPMG – General Purpose Machine Gun
After World War II, some engineers took a look at all the machine gun options and realized that they could come up with something that balances all available capabilities. Germany's MG34 and MG42 were the first GPMGs to emerge. Today, just about every country uses these.
Lance Corporal Kendall S. Boyd (left) and PFC Ryan J. Jones (right), combat engineers, Combat Assault Battalion, 3rd Marine Division, hone their machine gunnery skills by firing the M240G medium machine gun in 2004. Note the rivets on the receiver. (USMC photo)
SAW – Squad Automatic Weapons
Also known as LSWs, or Light Support Weapons, these weapons emerged as a problem was discovered with the GPMGs. GPMGs typically used ammunition of a different caliber than ARs and LMGs. SAWs use the same type of ammo as the rifle squad, making it an efficient, potent choice. A modern example is the M249 SAW.
A U.S. Marine fires an M249 light machine gun. (U.S. Marine Corps photo by Sgt. Donald Holbert)
HMG (Modern) – Heavy Machine Guns
The modern heavy machine gun packs huge amounts of stopping power with .50-caliber rounds. For examples of the modern HMG, think Ma Deuce or the Russian DShK.
Marines with Company A, Infantry Training Battalion, School of Infantry-West (SOI-West), fire the M2A1 .50 caliber heavy machine gun as part of their basic infantry training Sept. 20, 2016, at Marine Corps Base Camp Pendleton, Calif. (Official Marine Corps photo by Lance Cpl. Joseph A. Prado)
For more details on how to tell which type of machine gun you're admiring, watch the video below: