Just lately I have found Several uppers which might be choose offs from rebuilt M16A1 rifles remaining offered as "new substitution uppers". Individually, I would not make use of a drill push. It could be done, but I'd go the router or mini mill route. A lot of the registered Design 01's I do know of were current in the manufacturing unit pre

Wound up with that higher and It is chrome bore barrel in the future.  I do think It is an A1E1 from some nomenclature I saw but not sure as I've never observed A different one. I figured this was made around the time of item advancement towards the M16A2 ?. I can perform photos  if requested .... effectively I tried, but this site would not do i