MiniBalls are the term civilians give to railguns due to the fact that the projectiles are so small. Conceptually simple, railguns use an electric motor to accelerate conductive projectiles. Railguns have awesome piercing potential in all their forms. All mass driver weapons, at the end of the day, are merely forms of railguns.
Railguns remain potent weapons. When people think of mass drivers they think of bullets. But that's really not the full story.
MiniBalls make use of alumninum-based projectiles that are fired at a relatively low rate . Despite this, against ships with little armor, this form of railgun can be devastating.