A full metal jacket (or FMJ) is a bullet consisting of a soft core (usually made of lead) encased in a shell of harder metal, such as gilding metal, coppernickel or less commonly a steel-alloy. This shell can extend around all of the bullet, or often just the front and sides with the rear left as exposed lead. The jacket allows for higher muzzle velocities than bare lead without depositing significant amounts of metal in the bore. It also prevents damage to bores from steel or armor-piercing core materials. The appearance of FMJ ammunition is highly distinctive when compared to hollow-point or soft point bullets. The FMJ round has several advantages, first off they do not expand making them more effective at piercing armor. Next, they are more durable and withstand rough handling on the ba