I have read all of the replies and your OP several times. Going from satisfactory performance to not hitting paper at 20 yards just does not add up. I did not read anywhere about how many rounds you have put through this rifle over the past four years, nor did I read anywhere about what kind of ammunition you have put through the rifle as well??? As some have written in replies your barrel "could" be fouled up, however I believe that there is a mechanical issue that is causing your rifle to not hit paper at 20 yards, and.... not the stock as you have suggested. When I read a thread such as this one, I always start with going back to the basics, starting with the mounting of the sighting system on the rifle as well as the scope itself. A few years back I had a friend who was in a panic. He had a week before he was to go on a hunting trip to Wyoming (?) on a combination mule deer/antelope hunt. We live in Rhode Island and this was to be a hunt of a lifetime for him. He wanted to try shooting his rifle out to 300 yards due to the distances he felt he was going to be shooting at. When we got to the range he started shooting at targets at 100 yards and his groups opened up to 2-3+ inches. The rifle was a Winchester model 70 in .270 WSM and always was a tack driver. Talk about sweating, this was his primary rifle and a week before his hunt the rifle crapped out!! I started to closely watch him shoot, looking for something that he might be doing wrong. During his shooting I noticed that something moved on the scope. Upon the next shot I saw that the rear scope ring opened up at the junction where the top ring fastened to the bottom section of the scope's base. Upon close inspection the rear scope ring had cracked and was totally unnoticeable upon a regular visual inspection. If you would like to get out of the expense of a new barrel, you might want to consider a rebore to .338 Federal? If you decided to go the .338 Federal route I wouldn't be cutting the barrel as I would like to get as much horsepower out of that cartridge as possible to reach out 500 yards. A Barnes 185 MRX BT leaving the muzzle at roughly 2800fps out to 500 yards with a 200 yard zero would be 2 inches high at 100 yards, -8 inches at 300 yard with 2100fps muzzle velocity and 2200 foot pounds of muzzle energy, and out to 500 yards the round would drop 50 inches, have a muzzle velocity of 1718fps and have1440 foot pounds of energy. The expense for that would be around $250 and shipping. It ought to be a decent round for black bear hunting, not certain about an antelope cartridge out to 500 yards though? I have done several rebores from JES Reboring and have had nothing but good performance out of any of the barrels they have done for me. I have three 35 Whelens that were rebored on Ruger 77s from 30-06 and a BLR from .308 Winchester to .358 Winchester. Good luck with your rifle, but I would still be checking for a mechanical break down with the mounting/sighting system before I went any further.