full metal jacket

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, cupronickel or less commonly a steel alloy. An FMJ bullet is encased only on the front and sides, leaving the bottom as bare lead. Total Metal Jacket (TMJ) or Complete Metal Jacket (CMJ) bullets are totally encased. Totally encased bullets are not subject to exposing the bullet base to high-temperature gasses when the bullet is fired, thereby reducing the lead vapor generated. Thus TMJ and CMJ bullets are better suited for indoor firing ranges. The British overcame this by including a disc of fibreboard, similar to printed circuit board, over the top of the cordite charge and under the projectile of the .303 British ammunition. This also provide a rudimentary scraping or cleaning off residues in the barrel each time a shot was discharged. The use of full metal jacketing came as a result of the The Hague Convention of 1899, Declaration III, prohibited the use in international warfare of bullets that easily expand or flatten in the body. However, many states ban the use of non-mushrooming ammunition for hunting, since it is more likely to wound instead of kill. In general, a bullet 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 jacketed ammunition is highly distinctive when compared to hollow-point or soft point bullets. Historically, the first successful full metal jacket rifle bullets were invented by Lt. Col. Eduard Rubin of the Swiss Army in 1882. Full metal jacket bullets were first used as standard ammunition in 1886, for the French Mle 1886 Lebel rifle.