Jacketed Rifle Bullets
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. This shell can extend around all of the bullet, or often just the front and sides with the rear left as exposed lead. (A bullet that is completely enclosed by the shell is alternatively termed a total metal jacket round.) 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.
Because the bullets do not expand, they are more effective at piercing armor.
They are more likely to kill since they more reliably penetrate the body and reach vital organs.[1]
They are more durable and withstand rough handling on the battlefield.
Their rounded tips facilitate proper transit up the feed ramp, whereas the usage of hollow point bullets in some weapons may increase the chance of a failure to feed. Most modern weapon designs, however, will feed reliably with both types of bullet.
- Although British Mark 7 .303 ammunition is compliant with the terms of the Hague Convention, it creates more destructive gunshot wounds than standard spitzer bullets due to its internal design. The centre of gravity of the Mark 7 bullet is deliberately shifted towards the rear. This is achieved by constructing the front third of the interior of the bullet from a lighter material such as aluminium or wood pulp. The result is a tail-heavy FMJ bullet which yaws violently after hitting the target.
- American 5.56mm NATO FMJ ammunition has a much thinner jacket than others. As a result the bullet may yaw and fragment by fracturing along the cannelure, which is the groove running around the circumference of a bullet and is used to crimp it to the cartridge case.
- Russian 5.45x39mm FMJ ammunition uses a tail-heavy bullet which has a tendency to yaw after hitting the target.
- German 7.62x51mm NATO FMJ has an unusually thin cannelure. When the bullet hits the target it fractures along the cannelure and fragments, causing massive tissue damage as per the 5.56x45 mm NATO bullet but on an even larger scale.