I stripped my M1A down recently to give it a good cleaning and reinstalled the flash hider which had come loose. I pulled the gas cylinder off also and scrubbed it out. I took it to the range today and was shooting about an 6" group high and to the right first, then about 3" high and to the left. It finally settled down to 4" high with the sight set to 200 meters and a tight group. I brought it down to 2" high for 200 meters and all is good now. It took about 10 rounds to get the rifle settled back from being taken to pieces đ. I think the flash hider and gas cylinder remove and reinstall were the biggest contributor to the crazy grouping.