The .50 Remington Navy / 13x21mmRF is a .50 in (12.7 mm) American rimfire handgun cartridge.
Introduced for the Remington Navy single-shot, rolling block pistol in 1865, the low-velocity round loaded a 290 gr (19 g; 0.66 oz) bullet over 23 gr (1.5 g; 0.053 oz) of black powder.
[1] The rimfire version was replaced in 1866 by a centerfire equivalent.
A Boxer-primed version remained commercially available until World War I.
[1] 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".