What are FMJ and Jacketed Hollow Point ammunition, and which is commonly used by law enforcement to reduce over-penetration?

• A. FMJ feeds reliably and penetrates; JHP expands on impact for controlled penetration and stopping; LE often uses JHP to reduce over-penetration.
• B. FMJ expands on impact; JHP feeds reliably.
• C. FMJ is designed for hunting; JHP is for practice.
• D. FMJ and JHP have identical performance.

Answer: (A)

Understanding bullet design helps explain why one type is chosen for duty: Full Metal Jacket rounds have a copper jacket over a lead core that tends to stay intact on impact, so they penetrate deeply with less deformation. Jacketed Hollow Point rounds, on the other hand, are designed to expand when they hit a target. As they expand, they increase in diameter, transfer more energy to the target, and slow down sooner, reducing the likelihood of passing through the target.

For law enforcement, this combination matters: expanding bullets change shape and slow inside the target, which increases stopping effectiveness while reducing the chance of over-penetrating and potentially hitting bystanders. That balance—effective stopping power with controlled penetration—is why jacketed hollow points are commonly used for duty ammunition. FMJ can penetrate more deeply and predictably, but that deeper, less-deforming penetration raises the risk of through-penetration.