A kinetic ram for a blowout preventer includes a pressure chamber having a piston movably disposed therein. A gas generating charge disposed at one end of the pressure chamber. A ram is coupled to the piston on a side of the piston opposed to the gas generating charge. The ram is arranged to move across a through bore in a blowout preventer housing disposed at an opposed end of the pressure chamber. An initial volume in the pressure chamber between the one end and the piston is chosen to limit a maximum pressure caused by actuating the gas generating charge to a predetermined maximum pressure, and/or the pressure chamber comprises a pressure relief device arranged to vent pressure in the pressure chamber above the maximum pressure.