I just ordered a RRA varmint AR with a 20" barrel with 1 in 8 twist. I'll be shooting coyotes out to 275 yards. I guess I have two questions. First what is the minimum weight to properly stabilize a bullet with this twist rate?
What would be a good hunting bullet for 'ol Wylie Coyote? Thanks....

Other than the 75gr AMAX, there aren't any bullets over 60gr that I'd be shooting varmints with. I would try 60gr Sierra HP or the 50-55gr plastic tip bullets. They should all do well in your 1/8.
The other 75-80gr bullets should shoot well in your rifle, but they are useless on game. Come out and shoot a Highpower match if you want to use those.

I'm having Krieger cut me a barrel through which I will shoot .22 sabots with 55gr FMJs as well as .308 cal FMJ and HPBT slugs NTE 165gr. I specified a 1:9 RH twist in the order, but was told by Frank Green at Krieger that the .22s would stabilize with a 1:12 or 1:14 rate and that the .308s would work best with 1:10. In the end we went with the 1:10. It would seem that twist rate and weight are related and the lighter the bullet, the slower it can be rotated to affect stability. This is why .22RF guns have rates up around 1:16. So can somebody tell me why .223Rem guns have rates as low as 1:7.5?

my 1 in 8 pacnor will stabilize bullets to the 80 grainers from sierra or nosler. this is on a Ruger 77 Mk 2 action, with a 24 inch heavy sporter stainless steel barrel with a hogue rubber stock and a Weaver V 16 scope.

the only ones it does not like is 77 grainers. don't know why, because it loves the 75 grain Hornady's, A max and HP. and the 80 grainers.
Guess it is like someone liking this brand of pop and not this one.

rootbeer, the faster twist rates are for bullets that are longer. Compare the length of an 80 grain 22 cal bullet to a 40 or 50 grain one. I also shoot a lot of 6.5 mm. Even tho it is popular to do a 1 in 9 twist, the older Swedish Mausers used a one in 7.5 twist. One several rebarreled rifles, I use a 1 in 8 twist. they have proven more accurate than the one in 9 twists, even with the lighter bullets.

Hey Rootbeer!
The latest thing in .223 Remingtons is a 1/6.5 twist! That's so you can shoot 90gr bullets at 1,000 yards.
The 1/7 twist barrels started out as a military thing so they could shoot tracers, I think M856. Those things are about as long as a darning needle, even longer than Sierra 80s. Other than that, these quick twists are for Highpower Match shooting at 600 yards and longer. There aren't any hunting bullets that can use that kind of twist. (Well, OK, the Hornady 75 AMAX, but it's not really a varmint bullet. It's intended to be a match bullet and just happens to be good for varmints)