I have a Model 1 sales AR with a 24" fluted bull barrel. I only have a couple of hundred rounds (maybe) through the barrel. Couldn't get it shoot a group with BUIS, we kept raising the front post but it just wouldn't put what I call a group on paper. Later discovered that they make two heights of front posts one for the gas block (which is what I thought I had purchased) and one for the hand guard where mine now sits untested. Also mounted an enexpensive 4 power scope on the flaptop upper, went too the range and got it sighted in more or less. At this point I don't know what I need to do to get it shoot somewhere near its potential. 1) Have shot a couple of different brands of ammo. 2) Get much better optics maybe the stadia lines are to big (MOA) to get a good group. 3) Clean the barrel better between outings possible the barrel isn't broken in yet. I know I am older and am have trouble with my eyes but it doesn't seem to effect my ability to shoot a group with my 308 Saiga or my 300 WIN MAG Savage. This thing shoots more of a pattern than a group.