When you say "vise", I am assuming you mean a shooting rest of some sort. IF you are actually shooting from some sort of vise, that could be the source of the problems. NO rifle will shoot well from a hard surface or vise. Use a cushion between your rifle and the rest.

You have to clean these things from the muzzle, so rifling can get worn at that point. This is bad for accuracy.

The BAR I had (.308) would put two shots right together, then they'd walk off vertically. It was a Grade IV, so was nicely engraved. Too bad it wouldn't shoot. Got rid of it.