RazorGun Rubberball Speed Ball .50 Caliber 500pcs (337-041) - Target Shooting 2,138.20 CZK 1,924.38 CZK .50 Caliber rubber bullets for use with paintball markers such as the Umarex HDR 50 and HDP 50. BUY Share Article Number: 3623 Information Reviews .50 Caliber rubber bullets for use with paintball markers such as the Umarex HDR 50 and HDP 50.