Metabreaker now allows you to select general ammo quality, if you were looking to shake things up but still keep them reliable. Why was Bubba allowed to make his Pissin' Hot Hand Loads for SEAF-grade ammo? Why does it interface with selectable ammo types, implying Bubba can make napalm and nuclear plasma? The answer is simple:
It ain't that kind of movie, kid.
Also, damage scales recoil, so the gun that hits hard kicks hard too.