Well,.................
Don't know if this will help or not, but my Son's unit has M16A4's. Just like the A2, but with a removable carry handle. 20" barrel, standard butt stock, semi and 3 round burst. Son is his unit armorer, and he has seen the A3 version in a 20" rifle, with a removable carry handle and full auto selector. The A3 is basically based on the A1. He has also seen the M4A3 which he assumes is a SOF weapon with removable carry handle, 16" M4 barrel, collapsable stock, and full auto selector. His unit is supposed to get some M4A2's (semi only) soon also. I think you can't keep up with this stuff without a Program!:banghead: