It should be noted that the M-16 family of
weapons all spring from the original AR-10 design. The AR-10 was chambered for
7.62 rounds, featured a heavier
barrel, and lacked a forward assist (allegedly because it was not needed). The AR-10 looks like a slightly larger M-16. A
civilian version is still produced with a semi-automatic fire rate.
Rumor has it that the
Air Force was originally interested in the
rifle but asked that it be rechambered for 5.56 (.223) rounds for
training purposes.