Full metal jacket (ammunition)

These .30-caliber (7.62 mm) full metal jacket bullets show the typical jacket openings exposing the lead alloy core on the base of the bullet to illustrate that a full metal jacket may not completely enclose the core.

Examples of FMJ bullets in their usual shapes: pointed ("spitzer") loaded in the 7.62×39mm rifle and round-nosed loaded in the 7.62×25mm pistol cartridges

A full metal jacket (FMJ) bullet is a small-arms projectile consisting of a soft core (often lead) encased in an outer shell ("jacket") of harder metal, such as gilding metal, cupronickel, or, less commonly, a steel alloy. A bullet jacket usually allows higher muzzle velocities than bare lead without depositing significant amounts of metal in the bore. It also prevents damage to bores from hard steel or armor-piercing core materials.