The .300 Winchester Magnum, also referred to as .300 Win Mag or 7.62x67mm was developed and produced by Winchester Repeating Arms in 1963. The 300 Win Mag is special because it is a magnum cartridge designed to fit in a standard rifle. Because of the design of the 300 Winchester Magnum round’s versatility, it has become a widely popular round for hunting, target shooting, law enforcement, and long range marksmanship.