Atomic Ammunition Atomic Ammo .300wm 220gr. Match Sierra Hpbt 20-pack. This ammunition is designed for match target and tactical use the bullets loaded may not be appropriate for use in hunting big game. Specifications for Atomic Ammunition Atomic Ammo .300wm 220gr. Match Sierra Hpbt 20-pack: Manufacturer: Atomic Ammunition Caliber: .300 Winchester Magnum Number of Rounds: 20 Bullet Type: Jacketed Hollow Point (JHP) Bullet Weight: 220 grain Cartridge Case Material: Brass Muzzle Velocity: 2600 ft/s Primer Style: Centerfire Package Contents: Atomic Ammunition Atomic Ammo .300wm 220gr. Match Sierra Hpbt 20-pack