you could try seeing if the scope has parallax in it at 100 yards, could be your first shot is off due to where your eye is relative to the ocular. Then shoot a 5 shot group single loading followed by a 5 shot group from the magazine, see if you have two groups. I would clean the chamber first.
Frankly my solution in the past to this problem is to sell the rifle if you get two groups from single loading and magazine loading.. I am not smart enough nor have time enough to fight something like that....
