Thank you everyone for the info.
First, 1:9 twist rate is a slower twist rate, 1:8 is a faster twist rate and 1:7 is the fastest (current) twist rate
You're right. I don't know why I mixed them up when I posted the question. I knew that 1:7 was faster than 1:9, but thank you for bringing it to my attention.
As usual you are a wealth of knowledge. Thank you for help.
Meaning a 1:7 can shoot 80-90 gr bullets, but it will also work with 50 gr bullets.
A 1:12 will stabalize the 50-55 gr bullets but will not stabalize the heavier bullets.
From your post I understand that a 1:7 (or the fastest twist rate) will give you a wider variety of bullet weights that you can use over slower twists. But would a 1:12 twist be better for say a 55gr 5.56 than a 1:7 in terms of (all else being equal) groupings and accuracy? You just wont get the same performance from a 80-90gr compared to using the 1:7. It seems (and I'm learning here) that if I wanted to strictly target shoot with 55gr, I would be better off with a 1:12 rather than having a more versatile option with the 1:7.
^I hope that makes sense.
And for what its worth this is only for my knowledge, I'm not looking into buying another AR just yet. But on mine I have a BCM 16" mid with a 1:8 twist. I don't target shoot and I use 55-62gr ammo.