When speaking of the original AR10's, they originally were a bit backwards from other battle rifles of the era in that they had aluminum barrels and steel magazines. Later, they decided to go the other way around and used steel barrels and aluminum magazines, although many would later say that they really should have stuck with the original steel magazine design; it was a much better design. I've shot both and I would have to say that if I were relying on the AR10 for anything, then make mine a steel magazine.
