Oh right... I actually changed that years ago on a local copy after finding the excellent IMFDB article on the M16 rifle series (http://www.imfdb.org/wiki/M16_rifle_series
) but never got around to posting it.
One correction I might add to your M16A1 is to thin the barrel out a bit - it's still using the same heavy barrel from the A2.
Do me a favor and maybe put "A2 receiver modified by Brian" or whatever on the parts sheets.