THis chart that keeps popping up in many people posts is the opinion and a little research of ONE man (rob_s) http://www.tacticalyellowvisor.net. not any company standard chart. just his opinion of the AR15 M4 rifles he has tested. which are inaccurate in some ways. I have a bushy and his chart says it doesnt have a properly staked gas key which I compaired with a friends colt to be identical. some people on this forum swear by this chart with no hands on expierence with more then one or two of the rifles on the list. One guy one here named Tim says Colt is the golden standard, everything else is crap. yet my "crap" out shoots the golden standards every weekend at the benchrest range. Go with what you know or have had your hands on, or what feels good in your hands, and most of all what You really want, not what some chart made up by one guy tells you is the best AR.