what does the hmr stand for in .17hmr
.17 HMR .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. Commonly loaded with a 17 grain (1.1 g) projectile, it can deliver muzzle velocities in excess of 775 m/s (2550 ft/s).[3]