I have a heavy 223ai built on one. Feeds awesome and I like the mechanical ejector. I did have the screw that holds the bolt stop in break on me about 600 rounds in. Thats the only thing I can cuss about it. They have a heavy duty bolt stop that is held in by a screw on the side instead of underneath. I'd go that route from the get go if possible. It takes just a tiny bit of relief of the top of the stock.