Build it and it will shoot
DSC 223, build it and it will shoot. I've never had an AR out past 300 so i don't know but i've shot em out to 300, my buddy last summer placed 2nd to me in the sierra match at borden, he beat out 12 other experienced shooters with his (mine now) Rock river piece 24" 1-8 using factory federal 77gr'ers.
Another buddy I shoot with has an old Colt Sporter II , he has a second upper with a shilen target barrell on it 1-9 twist, it took me almost a year to get the perfect load for it. After someone laughed at me for posting thumb tacks as targets one day he shut up after watching me smack 3 of them with consecutive shots, (i chickened out and didn't attempt the 4th) He said it couldn't be done as well glad he was there to watch. Rifle has a cheap 32x Simmons scope and it also has a match trigger.
Load was 68 gr. HPBT Hornady's in front of 22.1 gr. of H335.... 22.1 gr. of IMR 2230 works well too.
M.