Never had or seen or heard of M16AI with a selector switch for (3) shot while I was in the Marines. The Marines changed to the M-16A2 in 1983 with a 3 shot selector, and the Army in 1986. The official story was for better fire control. However, the real story is for ammo consumption. There was a study after VN and it was determined that 56,000 rounds were fired to take one enemy. We lost 56,000 Service People in VN and it took us 56,000 rifle rounds to kill one NVA/Viet CongI wonder where you got your info from. There wasn't any 3 shot m-16 in Vietnam that every saw. I don't even think I would want one anyway. i can just see it. Trying to open up and 3 shots you stopped. have to depresss the trigger again.