A railgun uses magnetic forces or other frictionless force to push a projectile at extreme speeds. Compared to projectiles propelled through compressed explosive means, these shots have an incredible amount of force with a small amount of recoil. They scale upwards in a hideous fashion – the largest ship railguns have such incredible kinetic force that the impact is much stronger than most nuclear weaponry.
The primary downside to weapons of this nature is that ammunition usually occupies a substantial physical space and power requirements tend to be astronomical.
Some models rely on tiny slivers or shavings off of a block of metal instead of rods, which are more common. These have much smaller power requirements, but suffer from problems with overheating if fired for prolonged periods. Additionally, these models are capable of firing extremely quickly, though accuracy is much worse and the impacts caused by the projectiles are insignificant comparatively, they can be completely devastating to personnel or unprotected systems.