For a straight barrel, you can just turn it around... however, when you start inletting swamped barrels, this doesn't work as the swamp in the barrel is not uniform down the length of the barrel.
In that instance, you must remove the breechplug to inlet the rear of the barrel. I don't have a big vise, just a little one, but I was able to mount the rear of the barrel in the vise padded with leather, apply a large crescent wrench to the bottom of the breechplug, and give the end of the wrench a couple of smart whacks with a rubber mallet to break the plug loose. As long as you keep the tips of the wrench below the very top of the tang, you'll only slightly booger up the bottom part of the plug that sits down inside the stock and won't be seen anyway.