I just purchased this firearm today and put a Burris fulfield II scope 4.5-14 X 42 scope on the rifle. I went to the range to sight it in, starting a 50 yards, I couldn't hit the paper so I went to 25 yards. Got it initially dialed in at 50 yards, but it was way off at 100 yards, after firing 20 rounds, approximately $60 worth in bullets, I noticed the muzzle brake was moving slightly closed nearly everytime the gun fired. This caused a change in pressure in the barrel which caused the bullets to fire inconsistently. The adjustable brake doesn't seem to have a set screw or anyway to tighten it in a position. There is too much play in it and it doesn't want to stay open. Does anyone have any suggestions on what to do about this?