asking for a friend of mine. He has a Tikka T3x in 223, the same rifle I have. His will shoot 1.5" groups at 200 yds and when he shoots to 300 yds his groups open to about 5 and 6". What can cause this to happen ? We have checked all bolts and screws, checked the scope mounting and even tried a different scope and got the same results. He did buy hie rifle used and have no idea of round count through his barrel. Barrel has been cleaned several times with Boretech Eliminator and the patches come out clean after a few patches of Boretech, nylon brush and more patches.