Mass accelerators propel solid metal slugs via electromagnetic attraction and repulsion. A slug lightened by a mass effect field can be accelerated to extremely high speeds, permitting previously unattainable projectile velocities.
The primary determinant of a mass accelerator's destructive power is length. The longer the barrel, the longer the slug can be accelerated, the higher the slug's final velocity, and therefore the greater its kinetic impact. Slugs are designed to squash or shatter on impact, increasing the energy they transfer to its target. Without collapsibility, slugs would punch through their targets while inflicting only minimal damage.
Rather than being mounted on the exterior, starship guns are housed inside hulls and visible only as gun portholes from outside.
A ship's main gun is a large spinal-mount weapon running 90% of the hull's length. While possessing destructive power equal to that of tactical nuclear weapons, main guns are difficult to aim. Because ships must be able to point their bows almost directly at their targets, main guns are best used for long-range "bombardment" fire.
Approximately 40% of the hull's width, broadside guns inflict less damage and can be mounted with greater numbers and more flexibility. The modern human Kilimanjaro-class dreadnoughts mount three decks with 26 broadside accelerators apiece for a total salvo weight of 78 slugs per side, firing once every two seconds.
However, mass accelerators produce recoil equal to their impact energy. While the mass effect fields suspending the rounds mitigate the recoil, recoil shock can still rattle crews and damage systems.