Carl Gustaf 20mm recoilless rifle

Carl Gustaf 20mm recoilless rifle, domestic designation Pansarvärnsgevär m/42, pvg m/42 (Antitank rifle /42), was the first blow-back weapon produced by Carl Gustaf stads The Carl Gustaf pvg m/42 fired the 20×180R cartridge which has two cutouts in the bottom of the casing. A seal covers these cutouts and when the cartridge is discharged, this seal burns away and some the expanding gases are expelled out the back of the cartridge. The locking block on the back of the gun, has a hole and the rear expanding gases escape out of this hole. The gases expanding out the barrel pushes the gun back and the gases expanding out the back, push the gun forward and in turn, cancel each other out, making this gun almost recoilless.