Back to the OP question- I have been shooting the same load of a 53gr HP Sierra flat base, same COAL, in various 223s with twist of 7,8,9, and 12" at 100yd only . Five shot groups. Overall, I'd say this particular load shoots about the same in all these barrels. I'm not seeing much difference even between the 7 and 12" barrels. The 9" twist barrel is a DPMS, and they (Luth) state this is the best all around if you are shooting the 55FMJ AND the 62gr 855/SS109 Greentip bullets. I think the 77gr Sierra is about the longest bullet that will still fit an AR magazine? But the 77gr requires the 8" twist?
