Two things that I would look at are how you pull the trigger and follow through. The mistake that a lot of fellows make is to try ti pull their trigger as if they were snapping off a shot at a running animal. When shooting from a support of some kind I keep adding pressure to the trigger until the rifle goes off, but do not know exactly when that will happen. You just slowly increase pressure until it goes off. The other thing is follow through, as the shot breaks and after, for a real second, you should look like a corpse, with absolutely no reaction. If you want to get an idea of what you are doing take a video from the side while you shoot your group(s). You can frame it tight so that it just shows your upper body. Finally, is your action bedded in your stock. If it is, have you checked the bedding with a dial indicator? Finally, do you have a rear sling stud on your butt stock that could be hanging up on your rear bag. and is the back of your pistol grip touching your bag either before or after the shot?