The current standard is the M16A2, which is teh carry handle version with updated sights and the "round" handguard ararngement vice the "triangular" version.
The M16A3 and A4 are both special issue weapons. I know the A4 is the flattie, but can someone remind me about the A3? I don't recall offhand...
The M4 is also known as the "commando," which should tell you who gets those. There are, as I recall, A2 and A4 versions - carry handle and flattop. Could someone please enhance my recall on this as well?
Frankly, tho, I'd like to see the AR10 as general issue and bring back the Colt LMG concept in .308 as well - would be an OUTSTANDING weapons arrangement for fire teams!
FFZ
Forgot - The M16A1 is also in common use with the ARNG - you should have been seeing quite a few in airports for about a year or so...
FFZ