My build.....AR build anyways.

Palmetto seems to only have 1:7 twist rates and 1:8. I'm trying to stick with a 1:9 for the 55 grain rounds.

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.