IMHO, it's hard to beat the .243 Win. for javelina. Nothing wrong with anything bigger than that either. I've taken them with a .223, and most of the time they work great, but if you had to take a shot at a trickier angle, the .223 might not always do the job. Yes - I speak from experience. Also, if you had to take a cross-canyon shot at a peccary (which happens quite often where I have hunted) and the wind is kind of stiff, I don't have the confidence of a 55gr bullet staying on-course vs. a 100gr or heavier bullet.
Having said all that, javelina hunting to me is an opportunity to get out and just enjoy. For me anymore, that means carrying my peep-sighted 30-30, or my Ruger Scout .308, or yes, perhaps a .223 in an AR platform. I have a friend who uses javelina season as an opportunity to use rifles that rarely come out of the safe - muzzleloaders, 375 H&H, etc. They all do the trick, and no, a 375 doesn't rip them in half.
Take what you want, know your limitations, and have fun!
