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· AC-556 Owner
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740 Posts
Oh! Thank you very much. So 1/7 doesn't like lighter rounds? Then they went all the way to 1/10 and then backed-off. What happened to 1/8 lol
1/7 barrels accelerate throat erosion. The problem is that the twist is too fast, and the bullets eat the rifling for the first inch or so near the throat. (At least that is what I've read on multiple tests of 5.56 barrel testing) A 1:9 twist barrel was a commercial fix to this problem. Likewise a 1:14 twist (I THINK it was 1:14 or was it 1:12) was not enough twist and bullets wouldn't stabilize properly.

If you have a 1/9 or a 1/10 twist barrel, you should be able to shoot up to 70 grain bullets without issue.
 

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57 Posts
1/7 barrels accelerate throat erosion. The problem is that the twist is too fast, and the bullets eat the rifling for the first inch or so near the throat. (At least that is what I've read on multiple tests of 5.56 barrel testing) A 1:9 twist barrel was a commercial fix to this problem. Likewise a 1:14 twist (I THINK it was 1:14 or was it 1:12) was not enough twist and bullets wouldn't stabilize properly.

If you have a 1/9 or a 1/10 twist barrel, you should be able to shoot up to 70 grain bullets without issue.
this as well,

i have better accuracy in my mini 14 with 1:9 with 55 grs or less, the max weight i use with good accuracy is a 62gr, with my 1:7 AR i use 77gr
 
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