This muzzleloader version of the X-Bullet is 100% copper with a large, hollow cavity for quick, sure expansion. Barnes Expander MZ Muzzle loader bullets produce more consistent shot-to-shot velocities and better accuracy than competing bullets deliver. The result. Greater shooter confidence and more one-shot kills. Expander MZ bullets deliver deadly performance at both high and low velocities. Expand to twice their original diameter, creating six razor-sharp copper petals that slice through game. No fragmentation - these tough, deep-driving bullets typically retain 100% of their original weight. 100% copper Exceptional accuracy Full weight retention Razor sharp cutting edges Double diameter expansion Deep penetration Effective at high and low velocities No fragmentation