So do you think I should stick with the 20 gauge slugs till I can find a bigger gun?
I would. You don't wanna be tracking a wounded, POed hog with a pop gun, trust me.
I'd be interested in knowing the difference in ballistics between that 30 cal and a 20 ga slug.
A foster slug in 20 gauge puts up 1600+ ft pounds IIRC. The .30 carbine, think of a .357 revolver with a 110 grain bullet.
Actually, it puts up close to 1000 ft lbs at the muzzle, just ain't much meat in the bullet. If using and expanding bullet, it's gonna be tough to get adequate penetration. I know, I know, head shot. Well, I could HEAD SHOOT a friggin' hog with my 10/22, but that don't make it an adequate hog gun.
Hogs require shoulder shots and a big boar will have a gristle plate there to penetrate plus all that muscle and bone. Nothing behind the shoulder, but guts. Don't go there. This is what makes 'em tough for the bow hunter, too. Inside 50 yards, the 20 gauge would do, the carbine, not so much IMHO. Me, I'll stick with my .308. You use what ya want.
A crippled hog will die eventually and every dead hog is a good hog around where I live, but I like to be able to put 'em down so I can carve 'em up and wrap and freeze 'em.