barrel twist which one


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Old 02-11-2009, 05:32 PM   #1
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Default barrel twist which one

I am looking to get an upper and would like some input on the barrel twist. It will be a 16" carbine upper and I have a choice of 1:7 chrome moly or 1:9 chrome moly twist ratio. This will just be a plinker. Any suggestions would be great.



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Old 02-11-2009, 05:46 PM   #2
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I have both. The 1/9 should be good to go for anything short of 70 gr bullets. IF, you want to shoot 70+ grain bullets go 1/7.

Either should be fine with the lighter bullets as long as you don't try to push "match" bullets too fast. The thinner jackets of the 50-55 grain HP's are likely to come apart at higher velocities (above about 3000-3100)



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Old 02-11-2009, 06:00 PM   #3
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From previous experience, here is what we recommend around the shop:

1:7 is not the best choice for the available bullet weights in common "retail" land....

1:7 is a faster spinning bullet rate, which means you have to shoot the heavier bullets out of them ( probably in the 77 grain, or higher, environment ). Most of the common civilian and military stuff is either 55 grain or 62 grain. With a faster twist rate, and the right conditions like high heat and low moisture, you could very easily overspin a 55 grain bullet and get it to particl-ize ( I made that word up ) and therefor would be useless in the field.

Now, if you were reloading, the 1:7 twist with the heavy bullets would give you great knock down potential over someone shooting the 55 grainers all day long.

So, basically plus one on what Robo said.

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Old 02-11-2009, 07:20 PM   #4
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1:9 for the 16in "plinker". Leaves more effective options for you with factory ammo.

Another +1 with robo and the fuzzy guy that used to be known as JD

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Old 02-11-2009, 10:54 PM   #5
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Quote:
Originally Posted by laynejc View Post
I am looking to get an upper and would like some input on the barrel twist. It will be a 16" carbine upper and I have a choice of 1:7 chrome moly or 1:9 chrome moly twist ratio. This will just be a plinker. Any suggestions would be great.
as stated above, IF you can find the heavier grain bullets in the new OBAMA-era, then I would go with the faster twist 1:7. that being said, you can still shoot the lighter rounds through it, just not the real light stuff.

Or go with the 1:9 and have a decent twist rate for everything from 45gr varmint rounds up to about 75gr, and you'll be pushing it at that weight.

OR...if you can find it, compromise and get the 1:8 twist and have the best of both worlds.

Slo


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