The ported barrel of the Welrod serves two purposes: it releases the powder gases gradually into the rear of the suppressor, reducing the sound of firing, and it reduces the velocity of the bullet to subsonic speeds (especially important in the 9 mm version since the standard 9 mm loading is supersonic). The metal baffles and rubber wipes that follow the barrel serve to further slow the gases of firing, releasing them over a longer period of time and avoiding the sharp explosion that occurs when high pressure powder gases are suddenly released to the atmosphere.