Quote Originally Posted by Ruiner
I know this, but I didn't want to go into detail. However, I do believe that M16A3, however rare, was fully auto as well.
Negative...

M16A1....full auto, non-removable carrying handle

M16A2...only change was that the full auto was removed and replaced with a 3-round burst selection

M16A3....New picatinny rail mounting system takes the place of the handguards

M16A4....removable carrying handle to allow for newer optics to be mounted on rail system