Consider this, take a 5.56x45mm/.223rem case, anneal it, open the front up to 9mm and launch 147gn 9mm bullets at something like 2200-2400fps (my estimate). It'd be legal for hunting in states that require straight wall cases and should be able to slap the snot out of a hog or deer or coyote and would be straight devastating against 2-legged varmints with 124gn pills at 2500fps. The bullets wouldn't penetrate deeply if they were non-bonded expanding type but the temporary cavity would be about the size of a basketball. Bonded bullets would be able to get much improved penetration but at those speeds I predict bullets would come apart anyway. FMJ's though would probably deform quite a bit themselves and still penetrate hard. I know about the .351WSL and it's kin and .358 Herret but those are really looking at using proper rifle bullets. I'm thinking about this as designed to use pistol oriented bullets similar to a .30carbine. In fact, this would be not much else but a bigged up .30carb though the pressure peak would be nearly twice as high meaning much higher performance levels.