There's a lot to be said for a short carbine, the M-1 Carbine was a wonderful design but shoots a pretty anemic round, the Marlin Camp Carbine in 45ACP was a good idea, but of limited capability, as it was a blowback design. Ruger's PC-4 seems like an improvement, if not for the godawful trigger, the one I shot was 20 pounds or better. But the owner had found 20-round magazines, and 20 rounds of 40 caliber hollowpoints at 1500 fps would certainly do in a pinch! Pretty much useless past 100 yards, but up close it's short, handy, and a natural pointer. One could do worse.
Personally, I think the 450 Bushmaster on an AR platform might be the ultimate answer......Jeff Cooper's "Thumper", a heavy-hitting semiauto. Terminal ballistics wouldn't be a concern!
Papajohn