The MG 131 was a German 13 mm caliber machine gun developed in 1938 by Rheinmetall-Borsig and produced from 1940 to 1945. The MG 131 was designed for use at fixed, flexible or turreted, single or twin mountings in Luftwaffe aircraft during World War II. It was also license-built in Japan for the Imperial Japanese Navy as Type 2 machine gun.
Maschinengewehr 131
13 mm MG 131 and 20 mm MG 151/20 ammunition
This is a list of firearm cartridges which have bullets that are 13 millimetres (0.51 in) caliber or larger.Length refers to the cartridge case length.
OAL refers to the overall length of the cartridge.
Bullet refers to the diameter of the bullet.
Example of a 13 mm cartridge, a .50-70 Government