UMAREX HDS T4E .68 CO2 black (7.5 joules version) The HDS 68 is a .68 caliber side-by-side shotgun with tremendous muzzle energy and a look that commands respect at first glance. Its easy-to-load double barrel holds two .68 caliber projectiles (rubber bullets, pepper bullets, chalk bullets and paintballs) that can be fired individually or simultaneously from both barrels.