When you say AC-556 what is AC. thanksWell the M-16 with that stock # shows sold, so I don't know how much they were asking. But, if you have the funds to get a Colt M-16, I'd say definitely go for it. The AC-556 has the benefit of factory support at half the price, so that's an attractive option. I wouldn't choose the 76 if I had the means for the other two.