XM913 chain gun

The XM913 chain gun is an autocannon designed for the US military, that fires a variety of munitions with a diameter of 50mm.

The weapon is a scaled up version of the 25mm bushmaster autocannon, used on the Bradley fighting vehicle, a variety of armored cars. A navalized version of the autocannon serves as the main armament of a variety of smaller vessels, as well as serving as a secondary armament on some larger vessels.

A chain gun is the name given to autocannons that rely on an external power source to cycle munition through the weapon. This is unlike man-portable firearms, and most other autocannons, which tap some of the expanding gases of each round to power the weapon cycling through to the next round. Chain guns allow the gunner to control the rate at which the gun fires. In addition more traditional autocannons stop when they get to a defective "dud" round. Externally powered chain guns skip past duds, and keep firing.

While the 50mm XM913 fires a larger round than its 25mm predecessor, the gun is only slightly larger, meaning that many of the exising vehicles that mounted a 25mm cannon can have it replaced with the (slightly) larger and more powerful weapon.