Coaxial weapon

A coaxial weapon is a weapon system that is mounted side-by-side with the main weapon system, usually on a tank.

Nearly all main battle tanks have a coaxial machine gun mounted to fire along a parallel axis to the main gun. Coaxial weapons are usually aimed by use of the main gun control. It is usually used to engage infantry or other "soft" targets when the main gun collateral damage would be excessive, or to conserve main gun ammunition. In some cases, especially on earlier tanks, ballistically matched ammunition was used in the coaxial machine gun to sight the main gun using tracer rounds.

An example of this kind of arrangement can be seen on the U.S. M1 Abrams main battle tank and the M2 Bradley fighting vehicle. The coaxially mounted weapon on these vehicles is the M240 machine gun, giving the tank commander a choice between using either the main gun or the lighter machine gun, as the situation dictates. The Russian BMP-3 takes the idea of coaxial weapons to the extreme, with both a 30 mm autocannon and a 7.62 mm PK machine gun mounted on either side of the main 100 mm gun.

Some recoilless rifles and rocket-propelled grenades use a coaxially mounted rifle to sight the weapon onto target. A modern day example of this is the British LAW 80 which has a small spotting rifle, mounted underneath the main tube, which can fire up to five pre-loaded tracer rounds.