Barrel, 22" .308 AR, Heavy Weight, Match Quality, FA by Criterion This might be a better barrell. So help me understand lingo please. For use on DPMS/Remington/FA pattern .308 AR rifles with a rifle-length gas system, includes barrel extension Can I go with a 13.8" trx extreme rail with low profile block. I am thinking so but not sure. Which gas block would you use on this setup?