The .260 Remington (.260 Rem, 6.5-08 A-square, 6.72×51.69mm) is an intermediate rifle cartridge which uses the .308 Winchester as its parent cartridge; the case is necked down to accept a .264 caliber bullet.
The .260 Remington started off as a wildcat cartridge - the 6.5-08. It was often created by necking down 7mm-08 Remington or .308 Winchester ammunition, or by necking up .243 Winchester brass to accept a .264 caliber bullet. Because of this, and the similar overall length (OAL), any weapon chambered for the .260 Remington can be converted to fire any of the aforementioned cartridges (.243 Win, 7mm-08 Rem, .308 Win, .338 Federal) with a barrel change.
The .260 Remington is created from the .308 Winchester; as such, the rim diameter is the same, and it uses a large rifle primer. The case is necked down to accept a .264 caliber bullet, and it has a case capacity of 53.5 grains. Out of a 26-inch barrel, the .260 produces a muzzle velocity of around 2860 feet per second.
The .260 Remington has a high ballistic coefficient, allowing it to travel longer with less drop and retain more energy downrange than larger, more powerful cartridges.