The .300 Winchester Magnum (known as .300 Win Mag) is a popular, belted

Belted magnum

The term belted magnum refers to any caliber cartridge, generally rifles, using a shell casing with a pronounced "belt" around its base that continues 2-4mm past the extractor groove. This design originated with the British gunmaker Holland & Holland for the purpose of headspacing certain of...

, bottlenecked magnum rifle

Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

 cartridge

Cartridge (firearms)

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

 that was introduced by Winchester Repeating Arms Company in 1963 as a member of the family of Winchester Magnum

Winchester Magnum

Winchester Magnum refers to a "family" of cartridges developed by the Winchester Repeating Arms Company , one of the oldest firearms manufacturers in the United States, in the late 1950s and early 1960s, all based on the same basic cartridge case...

 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.

The .300 Winchester is extremely versatile and has been adopted by many shooting disciplines.