My build.....AR build anyways.

dukeboy_318 said

my wife's PSA is 1:7 as is my DSA, I shoot 55's all the time, accurately. If you go with a 1:9, you'll limit your self to 55 gr and lighter, but if you go 1:8 or even 1:7, you can still shoot 55s, heck I shoot 40s with no problems but I can also shoot 77s.

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This is exactly correct. The slow twist will shoot light bullets ie less bearing surface, but not the heavier ones without more speed. The fast twist will stabilize more bearing surface as well as less. There is a margin to stay within but the 223 case isn't one to really worry about until you get into trying to stabilize the very long vld's.