These commonly available and cheap slugs work pretty good on pigs even from a 20 gauge. I use the discontinued Buckhammers in my rifled barrel slug gun mostly now but the Winchester 3/4 ounch rifled slug out of my 20 gauge Remington pump with an improved cylinder barrel worked just great on a bunch of hogs.

With the right shotgun they work great. With my 1100 and the IC choke, I can hold head shots on an IPSC target at 50 yards with plain box Winchester 1 oz slugs.