Twist Rate Question

That's the thing, it's all about the intended purpose. If you want to shoot prairie dogs with the 45-50 grain varmint ammo the 1:12 twist is optimal for that and will still stabilize the commonly available 55 grain stuff as well. The 1:8 sounds like a great compromise if you're mostly shooting 55gr+, but the 1:12 definitely has its place.

I read that really fast twist (like 1:7) can spin a very lightly constructed bullet apart. Seen that in a couple of gun mags, no first hand exp.

I heard from a few people here that there is an optimum twist rate for a particular bullet and it is possible for the increased RPM to hurt accuracy. This I've never understood.

Some of the really light bullets can fly apart if they're spun too quickly. I don't know if 1 in 8 is fast enough, but I'm pretty sure there are examples of 1 in 7 spinning 40-45 grain varmint bullet too quickly for it to maintain integrity. For my purposes, a 1 in 9 was a great compromise as it covered all of my shooting. It worked for a range of 45 to 69 and seemed optimal for 69gr, but that's all I tried. YMMV.

How heavy to do you want to go?
RT

I suppose my question really surrounds whether or not the faster twist (1:8) would not stabilize the light weight bullets. Meaning, what if I want to shoot the whole spectrum? As in, use it for both coyotes and as a backup (with the proper rounds) deer rifle.

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The 1:8 is perfect for the .223 /5.56 all the way up to 69gr. I don't understand why ever one wants the 1:7 when the most accurate target barrels produced for the AR15 are 1:8
1:12 to too slow for anything above 55gr.

I too have heard of 1:7 spinning apart lightweight varmint bullets but I have yet to hear a similar report about 1:8, though that twist rate has only recently become popular. I would think the 1:8 would shoot everything okay and be optimal for the 68/69gr stuff while still being very good with the 55-62gr bulk ammo and safe for the 45gr stuff. That's my educated guess on the matter anyway.

In other words, the 1:8 sounds right for you.

I thank the 1/12 if you are not going to use any over 65gr 1/9 75gr 1/8 80 gr 1/6.5 90gr. For 40gr up to 55 gr 1/14

Length, not weight. IMLE, a 1:9 will stabilize a 77gr SMK, but will not stabilize a 75 gr A-Max (a-max is longer).