I found that when I installed my PWS rail and then torqued the barrel screws properly (62 IN Lbs in an alternating fashion left side then right side starting from the back going forward) my groups tightened up a little. I dont know if they do this at the factory, i would think they do, and it is their instructions, however I do get better groups now. Seekonk makes a BT-2L T handle wrench that is set for 62 pounds and works well. Its a T-25 Torx bit BTW.