Colt-Mauser M2X Cannon

Colt-Mauser M2X Cannon is powerful semi-automatic fires full-size 20mm shells from an over-the-shoulder position. This allows for a long-travel recoil absorption rod. A 15+ BOD roll is required to avoid 1-2pts. of bruise damage to the firing arm/shoulder. A 4x telescopic sight is standard; the weapon weighs 23kg loaded.

Source

 * Chromebook Volume 2, pg.40
 * Blackhand's Street Weapons, pg.34