I got me the AR-10A4 flat top 16" barrel. Love that rifle, The accuracy out of that 16" barrel with ARGENTINE surplus is great 1/2" groups at 100 yards no problem.I can hit metal swingers at 300 yards,after that the 16" barrel is done. One draw back with my AR-10 is it rips the rim, especially noticable on commercial ammo to the point that some of it wont go into the shell holder. Military ammo is not so noticable. Checked around and have been told its the nature of the beast. Reliable as the sun coming up in the morning. Its a keeper.