Wait, this mod makes the fire rate of the Spas-12 super fast, but makes the reload as fast as the Mac-10, correct? If that's the case, it reloads one clip at a time, which is slower than the Spas-12's original reload time, making this mod similar to the shotgun to minigun mod, except with a faster reload time and slightly slower fire rate, right?
I really don't see the usefulness of shotgun mods in general except to completely fill a single enemy with holes, then run off to hide while you reload. It's really not very time-efficient unless you are up against a single high-hp enemy (such as the Super Spy).