.300 Win Mag

The .300 Winchester Magnum (also known as .300 Win Mag or 300WM) (7.62×67mm) is a popular, belted, bottlenecked magnum rifle cartridge that was introduced by Winchester Repeating Arms Company in 1963 as a member of the family of Winchester Magnum cartridges. The .300 Winchester Magnum is a magnum cartridge designed to fit in a standard length action. It is based on the .375 H&H Magnum, which has been blown out, shortened, and necked down to accept a .30 caliber (7.62 mm) bullet.