12.5 X 40 mm hand cannon made by the same people that make that revolver shotgun... TULA

12.5mm OTs-20 Gnom
smoothbore revolver

Intended for close-in combat.

It is chambered for special 12.5x40mm cartridges developed from a 32mm hunting cartridge case with steel and lead bullets and a shot shell.

Basic Characteristics
Cartridge STs110, STs-110-04, STs-110-02
Calibre, mm 12.5
Empty weight, kg 1.1
Firing mechanism double action
Cylinder capacity, rds 5
Overall dimensions, mm 250x132x45