FMJ

A Full Metal Jacket, or FMJ, bullet is encased in a copper-coated steel or gilding metal jacket. The encasing prevents the bullet from deforming when it strikes a hard surface. FMJ bullets are designed to go through hard surfaces such as armor without expanding or fragmenting.

It is one of the more common types of ammunition found in the Wasteland next to the 10 mm rounds. This and it's fair performance against both flesh and armor make it a popular choice with gunslingers. It is used by the Hunting Rifle, Sniper Rifle, and the .223 Pistol