What gun has 13mm rounds?

Answer 1

The M1918 Mauser T-Gewehr fired a 13.2x92mm cartridge. It was the world's first anti-tank rifle. In comparison, a .50 BMG cartridge is 12.7x99mm.

A large gun. That fires a bullet about a half inch in diameter.

Answer 2

The M1918 Mauser T-Gewehr fired a 13.2x92mm cartridge. It was the world's first anti-tank rifle. In comparison, a .50 BMG cartridge is 12.7x99mm.

Answer 3

A large gun. That fires a bullet about a half inch in diameter.