Twist Rate Question


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BridgeTooFar
February 10, 2012, 10:59 AM
If you can get a rifle in multiple twist rates (in this case, a T3 Lite in .223 with a twist rate of 1:12 or 1:8), why would you ever go for the slower rate (1:12)? I suppose if I know I'll only be shooting lighter bullets, maybe it would be ok, but if all the variables of cost are the same, why wouldn't I want the faster rate just in case I wanted to shoot the heavier stuff?

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gp911
February 10, 2012, 11:06 AM
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.

BridgeTooFar
February 10, 2012, 11:08 AM
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.

MtnCreek
February 10, 2012, 11:14 AM
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.

Red Tornado
February 10, 2012, 11:18 AM
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

carbine85
February 10, 2012, 11:21 AM
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.
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.

BridgeTooFar
February 10, 2012, 11:21 AM
Probably not anything above 68/69gr. if I had to guess. I'm just sort of spitballing a setup right now, and realized that the T3 came in both of those twist rates in .223.

gp911
February 10, 2012, 11:30 AM
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.

AABEN
February 10, 2012, 12:30 PM
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

MtnCreek
February 10, 2012, 01:05 PM
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).

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