Maybe California pigs are tougher, but the 5.56 works pretty darn well on Texas pigs!
I've only hunted pigs once in California, a trophy hunt for a big boar, and got lucky with a 250-pounder that had very good tusks. I used a .270, which might be a little better for a trophy hunt, but for general pig hunting the .223 works fine. At least that's my experience, as well as that of quite a few other people.
