I have a .44 Magnum that I use when hog hunting and will very effectively do the job, but a well placed shot behind the front shoulder, and a variety of calibers will bring them down. The skin in that area is not any thicker than that of a whitetail. The skin is thickest on the top side of the body and thins out some as it goes toward the belly ( have killed and skinned out a ton in my day) I killed a 185 lb sow with my .22 Magnum Taurus revolver. Shot was made just behind the front shoulder on the right side of the body. She hit the dirt and never moved!
If you let a hog get to a range of 18" you have got big problems.FairWarning said:I'd use at least a 6" barrel for .357. It really benefits from longer barrels, even out to 18"+.