THE ULTIMATE FMJ BULLET. Speer uses Uni-Cor technology to take full metal jacket bullets to their highest level of evolution. We completely encase the lead core in a seamless jacket. Other FMJ bullets have lead exposed at the base, or have an accuracy-robbing second piece to cover the lead. Those bases can deform under pressure. Our TMJ rifle bullets don?t foul barrels as much as traditional FMJ bullets and keep airborne lead to a minimum.