Originally Posted By: AlbertacoyotecallerWhat about going to the opposite way with lighter bullets. Looking for a barrel now for 40 -55gr bullets. Should I stick with a 1 in 12 twist or will the 8 twist still work?
With proper bullet construction, the faster twist rate barrels will stabilize light weight bullets, so yes, the 1:8 will stabilize a 40-55 grain bullet, as will a 1:12. The question probably should be "will a 1:8 twist rate in 223 using 40-55 grain bullets group as well as a 1:12 twist rate?" The answer probably is: "maybe".
I have a 1:7 twist AR and I tried 8 different powers in varying weights in an attempt to shoot small groups utilizing a 55 grain Hornady. The ONLY powder that consistently shot under an inch at 100 yards rested was CFE223 and ONLY with a load that was at max to 0.2 grain over max according to the internet published Hodgdon reloading data center. I gave up trying to find a sub MOA group using a 52 grain Berger in my AR.
Some people with AR's having a 1:7 twist rate seem to shoot any 50 to 55 grain bullet very well - but mine won't - yours might. Now I have a couple excellent accuracy loads using a 77 grain bullet, whereas an associate of mine with a 1:12 twist AR can't get a 77 grain to group consistently under 2 inches.