Okay, a new direction here:
1. Based on what you have said, you need a minimum of the .223 Remington. BUT: the .223 is loud, and I mean dang loud.
2. My thought? Get a lever action or single shot rifle, in .357 magnum, put a scope on it, and use the 180 grain factory loads. Sight it in for 150 yards. It should do fine on hogs out to that distance, but no further. Also, it is much quieter than the .223 and it won't travel a mile before it hits the ground..
3. If you aren't confident with the .357 mag, then do the same in a .44 mag. It will still be quieter than the .223. (It gives a nice round boom, instead of that ear-splitting high-grade sound-breaking crack!) Also, you can shoot the .44 special in it for closer shots, which is even quieter.
4. Good lever actions and single shots are very accurate in these two pistol calibers.
Just another option to think about.
Big Paulie