Have you ever toted an M-14 for any distance/length of time?
I have extensive experience with the 14, onboard ships and boats. I think it is a very good rifle, but I would hate to have to carry that beast in the boonies. In addition to that, as a gunsmith/armorer the M16/4 platform is much easier to service in the field and at the repair level.
I don’t have a lot of M-14 experience, but I agree that they were heavy and so was the ammo compared to the M-16. Our ground pounders are already wearing very heavy body armor, and I just can’t imagine dragging around an M-14 in that sort of situation.