I went last month, and had my Remington 742 in .30-06. Shot a smaller female right behind the ear, and down she went.

It was the first four-legged animal I've ever killed, and I was glad she went quickly. Never knew what hit her, I think. (Very tasty, too.)

I guess a .30-30 would've been fine, especially for a smaller animal, but you never know when one of the really big boars will turn up.