Ammunition Specifications Caliber: 10mm Auto Bullet Weight: 155 gr Bullet Type: HP XTP Muzzle Velocity: 1265 fps Quantity: 20 Rounds per box This Hornady Custom pistol 10mm Auto ammo is loaded with the famous Hornady XTP (Extreme Terminal Performance) bullet, which is supremely accurate, and delivers maximum knockdown power. Hornady produces most of the brass for Hornady Custom pistol ammo. All other brass is chosen to ensure it meets Hornady s unusually high standards for reliable feeding, corrosion resistance, proper hardness and the ability to withstand maximum chamber pressures.