I have a new M1A Nat. Match. I understand to break in the barrel must be cleaned of copper and other crud. I understand the drill and will do so for break in. However, on one of the shooting shows a military marksman was cleaning an M16. He stated that after cleaning the copper out he was shooting 1 to 1.5 MOA until after about 40 shots at which time he began shooting .5 MOA. He said to leave the copper alone until around 900 to 1000 rounds, and the MOA starts to fail. My undestanding is that fouling adversely affects accuracy of 5.56 or 7.62. Experienced comments would be appreciated.