The .475 A&M Magnum is a riflecartridge developed in the United States. At the time of its development it was considered the most powerful sporting rifle cartridge ever developed. However, as the .475 A&M Magnum was a wildcat cartridge, the .460 Weatherby Magnum continued to be the most powerful commercial sporting cartridge available.
The cartridge and rifle were designed by the Atkinson & Marquart Rifle Co. of Prescott, Arizona, by necking up the then new .460 Weatherby Magnum to accept a .475 in (12.1 mm) diameter bullet. Fred N. Barnes, the founder of Barnes Bullets for whom the first rifle chambered for this cartridge was made, supplied the bullets. According to anecdotes, Fred Barnes gathered a group of people to demonstrate the rifle. The rifle was fired at the base of a small tree which was uprooted while Fred Barnes who had been shooting from a crouched position on a gravel bed had slid a few feet and ended on his back due to the recoil.