17 HMR Ammunition

17 Hornady Magnum Rimfire (4.5×27mmR), commonly known as the .17 HMR, is a rimfire rifle cartridge developed by the ammunition company Hornady in 2002. It descended from the .22 Magnum by necking down the .22 Magnum case to take a .17 caliber (4.5 mm) projectile.