The .50 Remington Navy / 13x21mmRF is a American rimfire handgun cartridge.
Introduced for the Remington Navy single-shot, rolling block pistol in 1865, the low-velocity round loaded a bullet over of black powder.
The rimfire version was replaced in 1866 by a centerfire equivalent. A Boxer-primed version remained commercially available until World War I.
The power of the .50 Remington was less than average, but the heavy bullet, even at comparatively low velocity, made it "a rather potent handgun round".