I bought my 556 about a year ago and I'm very happy with it. It's very reliable and looks cool as hell but there are some draw backs. I originally bought the classic patrol but soon added a Troy quad rail, magpul ubr stock. The aftermarket parts are pretty limited and I had to modify an AR pistol grip for the sig. It's pretty heavy but I added a lot of weight to it. Great alternative if you want something different than everybody's AR. One big flaw IMO is that the casings eject and hit the frame behind the charging handle. This scuffs the metal up a bit but also puts a good sized dent in the casing so if you reload your .223 brass you won't be happy.