Has anyone heard of an XM-21 or M-21? a super accurized M-14 was more reliable and dependable than the bolt-gun platform in Vietnam. The SR-25 from Arma-Lite is a hyper accurate AR-10 platform, We have hyper accurized 10-22's, Mark 2,3,4's, there are whole parts of certain custom gunsmithing companies devoted to make hyper accurate semi-auto firearms. I own a hyper accurate M-1A (M-14 platform in semi-auto) nothing says a bolt gun is the only accurate platform. every since the 1960's the semi-auto has been a competing platform for super accurate, hyper reliable precision rifles. if you want to make your AR hyper accurate for a bit less than you expect. look up Brownell's on the net and get one of their house brand barrels for your AR, whether it be a 15 or a 10. these barrels are R-5 rifled Satern barrels. I own one and have been putting them on all my custom AR builds for clients. My personal gun can keep a 10 shot, .243" Dia. hole at 100 yards with 75 grain A-max or 75 grain match kings. BLC2 is the best powder I have found for my rifle. the gas system is a medium length so a slightly longer burning powder is needed to operate it. the best groups, most consistently accurate round is the 68-69 grain match bullets with BLC2. standard 55 grain over the counter ammo keeps less than a 3/8" group all day long. when you put one of these Brownell's barrels on, or have a gunsmith do it.. specify the torque range. the secret that Colt has is that they use a different torque on their match rifles. the range for match and precision is 28 foot pounds to 32 foot pounds of torque on the barrel nut. they also use an automotive product on the barrel nut's thread, it is silver/high temp "anti-sieze" found at your local auto parts store (NAPA specifically). you need to torque and loosen the barrel nut 3 times before a final torque. this is something passed down to me from MMU 'smiths and more than one custom AR builder. this technique works very well and over time you only loose 1 foot pound of torque. this is contrasted with as much as 10 foot pounds dry and one torquing.
later tatters.