Soldiers fire .50-caliber machine gun rounds at the base of a training target to indicate to nearby helicopters where to fire their rockets during partnered aerial-ground integration training between US and Iraqi forces.
Marines from 2nd Battalion, 1st Marines, 11th Marine Expeditionary Unit, fire M240G medium machine guns at fixed targets in Djibouti.
Tracer rounds contain flammable materials that ignite and produce a bright (but deadly) trail of light towards a target. Intended to guide the shooter during adverse conditions, they can prove to be extremely valuable during low-visibility scenarios.
Due to the fact that an enemy can potentially see where the shots are coming from, they are normally used sparingly — often distributed between several normal rounds.