I've noticed that some companies have quit making 11.5" carbine barrels while others don't make carbine barrels shorter than 11.5". A local Gunsmith advised that my new upper that I'm building be a 11.5" rather than a 10.5" due to reliability. Do 10.5" barreled uppers have that much of issue with reliability? I have been considering using a 11.5" barrel with an 10.75" URX 3.1.