Full Metal Jacket

Full metal jacket .303 British ammunition is a cartridge whose bullet has a hard outer jacket that does not expose the bullet's lead core. This hard outer jacket enables the bullet to deform very little when hitting its target. This style of FMJ bullet leads to much less damage to the target than other projectile designs. Since the .303 was originally a military cartridge, it most common bullet design was the full metal jacket. This fact was due to the rules of military engagement requiring a bullet which caused "less damage" when used on humans in military conflicts.

At one time, the military actually used a non-full metal jacket round but dropped is use because of the significantly higher damaged caused by that bullet in combat. One can still obtain factory ammunition with full metal jackets in various bullet weights, even the original 215 grain offering.