Animation: How a M249 SAW Light Machine Gun works

M249 SAW Light Machine Gun

The M249 SAW (Squad Automatic Weapon), formally written as "Light Machine Gun, 5.56 mm, M249", is the US military’s adaptation of the Belgian FN Minimi, a light machine gun manufactured by FN Herstal (FN).

The M249 SAW is manufactured in the United States by the subsidiary FN Manufacturing LLC, a company in Columbia, South Carolina (FN America), and is widely used in the U.S. Armed Forces.

It was introduced in 1984. The M249 SAW provides infantry squads with a high rate of machine gun fire, combined with the accuracy and portability of a rifle.

The M249 SAW is gas operated and air-cooled, it has a quick-change barrel and a folding bipod.

The SAW can be fed from both linked ammunition and STANAG magazines (such as those used in the M16 and M4).

The M249 SAW has seen action in major conflicts involving the United States since the U.S. invasion of Panama in 1989.

In 2009, the United States Marine Corps selected the M27 Infantry Automatic Rifle to partially replace the M249 in USMC service.

In 2022, the U.S. Army selected the SIG Sauer XM250 to replace the M249 SAW.

It fires from an open bolt and is gas operated. When the trigger is pulled, the bolt and bolt carrier move forward under the power of the recoil spring.

A cartridge is stripped from the belt, chambered, and discharged, sending a bullet down the bore.

Expanding propellant gases are diverted through a hole in the barrel into a chamber.

This pressure moves a piston providing the energy to extract and eject the spent casing as well as advance the belt and compress the recoil spring, thus preparing for subsequent shots.

The M249’s air-cooled barrel is equipped with a mechanism to remove and replace the barrel assembly with a spare, this makes it easy for the operator to easily change the barrel on the field when it gets too hot during extensive amounts of fire.

The M249’s original gas regulator featured two different gas port sizes; normal and adverse.

The normal gas setting has a cyclic rate of fire of around 700–850 rounds per minute, while the adverse gas setting increases the cyclic rate of fire to around 950–1,150 rounds per minute and is only used in extreme environmental conditions or when heavy fouling is present in the gas tube.

The two-position gas regulator was discarded as part of a product improvement program, which made the M249s that received the product improvement kit no longer able to fire at the higher cyclic rate.

The rapid rate of fire is around 100 rounds per minute. The sustained rate of fire, the rate at which the gunner can fire continuously without overheating, is around 50 rounds per minute.

3D Animation done using:

[jasonrad]

I love this gun but hated carrying it around🤣

[nobodynone]

It's a great video again but I also would haved liked to see It work with a STANAG magazine. But I always like to see your videos, it must be a lot of work.

[sambrowne]

Great vids. They show everything you need to see to understand how it operates. Only thing we didn't get to see is the internals operating at the actual rate of fire. Obviously slow motion is the only way to get a comprehensive look at things in action, but I think we should also get to take away an understanding of it's full speed operation and an example of its actual rate of fire.