• This cartridge pushes the limits of pressure possible with a rimfire case. Also referred to as the .22 WMR, the .22 Magnum was initially offered with 40 grain FMJ and JHP bullets at an advertised muzzle velocity of 2000 fps from a rifle barrel and 1550 fps from a pistol barrel. Due to the high supersonic velocity, .22 WMR cartridges are loaded with jacketed bullets. The various 30-40 grain JHP bullets are best for varmint hunting, but are overly destructive on small game.