Hello Jasper, I 2nd BR on the action issue.
Make sure that things are sitting right, (unscrew the tang and see how high it rises. If bedded properly, in theory, it shouldn't) Do this with the rifle standing up so that the weight of the barrel doesn't pull the tang up.
Make sure that the bottom metal DOES NOT TOUCH the action. If it does it can spring the action from the inside in which case you really aren't using the bedding.
Make sure that the screw holes are clear all around so they aren't acting as a recoil lug.
If you are still having problems, stick something under the foreend supporting the barrel and see if your accuracy improves. If it does it is still a bedding issue or your barrel may be racked.
I have a Yugo 48 that I put together years ago in 6.5x55 that shoots into .5 or less. Plain Shaw barrel and a Timmeny trigger. Thats it. If it isn't shooting well, its me. I put another together in .450 marlin and that shoots into 1.5.
Cheers.
Tom