I had the privilege of meeting the late Hook Boutin who is probably one of the most famous and esteemed Armorers the U.S. Army has ever produced. He was on the team that designed all of the NM modifications for the M14/M21 in the early 1970's. He serviced and did match accurizing on my 1978 SA M1Aicon and a Smith Enterprise M-14 back in 2013 when he was 89 years old and still sharp as a tack. I flat out asked him which commercial receivers were the best in his experience working on them all for so many years. Bear in mind the SA Inc. is a casting, SEI forged from bar stock and LRB forged the same as the original M14 was. He told me the SA Inc receivers were the best. Thee was no hesitation or other questions asked so there you go. My M1A is now in M21 guise and on it's second barrel. I'd challenge anyone to hurt the receiver in a lifetime of use. Investment casting has also come a long, long way with quality control in the past 20-30 years. Food for thought.