The assault cannon is a weapon used near exclusively by Type II Dark Troopers. It is basically a bulked up, modified Imperial Repeater weapon. Four feet long, the wide stock has two barrels with two triggers. The first trigger fires a plasma shot, the second fires anti-personnel sized missiles. It carries enough ammo for 400 plasma shots and 20 missiles.
The Type III Trooper has a different, but similar cannon. It is essentially five plasma barrels on a single cannon and doesn’t fire missiles. Together, each shot sends very large blasts of energy. This particular cannon was too large and heavy for normal humanoids to carry.