The Hornady GMX (Copper Alloy Expanding) bullets offer the hunter who favors an expanding monolithic bullet a Better Choice. GMX bullets are constructed of the same copper alloy metal used to make ultra-consistent Hornady bullet jackets. Copper alloy metal doesn’t foul like “sticky” solid copper, and strategically located grooves in the bearing surface of the bullet reduce pressure. These additions make the GMX easy to load using standard published data for comparable Hornady SST bullets. Hornady engineers designed the GMX bullet to perform across a very wide range of velocities - from +3,400 to 2,000 fps. And perform it does. GMX bullets are designed to expand to 1.5 times their original diameter and retain over 95% of their original weight. They’re no slouch in the penetration department either, routinely penetrating over 30" in gelatin tests. This is not loaded ammunition.