Anyone know how to locate M16A1 S/N history? I'd like to know more about the one I carried in my time in service. S/N 4146832
There is no published criteria and Colt won't cough-up any information on M16's.
I got the date for my M16-A1 (S/N 6960xxx) by sending an FOIA request to the BATF.
Mine was registered by Colt on a BATF "Form 2" on June 8, 1983. A "Form 2" is a form submitted by a manufacturer.
You can't guess how new it is by the high/low-ness of the S/N either. They jump all over. Usually non-military guns (police, ...) are in the 9-million range and military in the 4-million.
Hope this helps.