AR Rifling Twist?

harbl_the_cat

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What's the deal with regards to the rifling twist for AR's? What's the twist for C7/M16 variants and how does different twists for different barrel lengths affect the performance of the rifle with varying ammunition?

Thanks, and sorry if this is beating a dead horse!
 
Well, twist is a matter for all rifles not just AR's, if the twist is faster you may use longer bullets (longer usually means heavier). Many like the longer range performance of the 77 grains bullets, and these may be stablized by at least a 1:8" twist. Most AR barrels twist are 1:7 1:9 or 1:12. So that is one reason why the 1:7 is loved the most, that and the as-issued aspect.
 
The 1:9 is the most popular for comertial AR's for us civies. It's a good all around twist for 45gr all the way up to 75gr bullets. It will also work for the 77gr bullets sometimes. I handloaded for two 1:9 twist AR's, same config, one with excelent accuracy and the other not so much. However they both grouped well with the 62gr and 55gr bullets, identical groups in size. I have since got a 1:8 twist AR and am loading the 77gr bullets with excelent result.
The C7 has a 1:7 twist.
 
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