My 7 x57 1A would walk them up off the paper with successive shots....fired 5 minutes apart. And it would not return to POA for hours.
I pulled the quarter rib and removed enough material to ge a .003 feeler gauge between the back of the rib and the receiver. Use lots of penetrating oil and soldering iron heat cycles before trying to remove the flat head allen screws securing the rib.....I broke the first one by being too hasty.
I believe if the rib contacts the front of the action that the rib moves/bends slightly when the barrel heats up.
This resulted in a major improvement, and a copper shim around the fore end screw promises some 1" groups. We'll see if I can repeat that.
