They inflicted damage by hurling projectiles at high velocities, which imparted kinetic energy and force to the target upon impact. Damage was thus a result of the mass of the projectile and its velocity.A mass driver projectile in space.
The velocity the projectile could achieve is limited by the method by which it is initially propelled. For a chemical explosion (how a conventional slugthrower works), the peak velocity was ~1.8 km/s. For a plasma driven round from an electrothermal cannon (an electrical arc vaporizes the propellant into a plasma to create the requisite pressure to propel the slug), the peak was ~2.5 km/s. For a gauss/coil gun (where the mass is accelerated by passing through sequenced electromagnetic fields) the limit was ~2 km/s due to the rate at which the fields can be created and collapse. These speeds are extremely small in comparison to light speed.
For a rail gun (where the slug is accelerated by Lorentz forces and electromagnetism between two parallel rails) there was no real limit (except the speed of light), only a practical one based on rail erosion and, when in atmosphere, ablation of the projectile. Typically this speed was 6 km/s.
Mass drivers were used to launch missile weapons carried internally, projectiles, and explosive shells. They could be found on a variety of craft from the missile launchers on the LAAT/i,[3] the siege weapons on the Dreadnought battle tank, the flak guns on most capital ships,[4] or serving as artillery on the AT-AP or the SPHA-M.[5]