Twist rate is a bit over hyped. I have made ARs with twists from 1-9" to 1-6.5". All barrels of very high quality shot extremely well and twist rate can't make up for lesser quality. For dedicated use of bullets from 70 grains and up, I'd probably go with a 1-8. But as of this writing my most accurate rifle firing 75 and 77 grain bullets has a 1-9" twist and does fine at all ranges. the old 1-12" and older 1-14" are too slow for very long bullets, but from 1-9 and faster you'll find little difference if all barrels are of high quality.
Remember the older Speer 70 grain semi-spitzers? I used a few thousand of them in an AR made in the 70s with a 1-12" and also a 22-250 with a 1-14 and they shot MOA in both rifles. Now that bullet is a semi-spitzer with a flat base to make it shorter then one of the long range bullets of today, but it's still not that short, AND it was designed to work in 1-12 and 1-14 twist rates. It did just fine.
This is not to say twist rate is unimportant. I am simply saying it's not AS important as bore quality. If you actually use bullet from 65 to 75 grains in a good 1-9" you'll see the same thing I see. It's just fine. So is 1-8 and 1-7
