What does FMJ mean ammo?

FMJ stands for "Full Metal Jacket," a type of ammunition where the bullet is encased in a hard metal shell, usually made of copper. This design helps improve feeding in semi-automatic firearms and reduces lead exposure during shooting. FMJ rounds are often used for target practice and military applications due to their reliable performance and lower production costs. However, they tend to be less effective for self-defense compared to hollow-point bullets, which expand upon impact.