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A buddy is building his first Grendel, he was looking at a barrel with a 1-9 twist.
It's my understanding that the 1-9 twist is better with lighter bullets, in theory anyway.
How would a 1-9 barrel handle the 129 & 130 gr bullets? Anyone have any first hand experience with one?
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BWild did a test with a J & T 1:9 twist 24" SS 6.5 Grendel which produced very good groups using the 139-140 bullets. Most resources I've looked at on 6.5/264 recommend 1:9 twist, a Friend has a Winchester 264 Magnum and has shot bullets from 85 Grain Sierra Varmint to 140 grain hunting bullets with no stabilization problems. Bill Alexander did a lot of testing and found the shorter barrels (<14.5-16") had better accuracy with a faster twist 1:8-1.8.5). Alexander Arms has sold 20-24" 6.5 Grendel's with 1:8 & 1:9 so I see no problem with 1:9. I have a 1:9 twist 16" J&T plus a 1:9 twist 20" SS Shilen with shoot great but I have not shot any bullets heavier than 123 grains. Personally I think the 1:9 twist will work.
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I have a AA 24" Overwatch 1/9 twist. Loves 123 g AMAX and have shot 140g Lapua Naturalis at 100 yds to about 3/4 MOA.
(Good enough for MY hunting!)
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Bwild97 had some 10rd groups with the 142gr SMK that were under 1/2 MOA, using his J&T 1/9 twist 24" barrel. Barrel length is related to this, because spin stability is affected by velocity. The higher the velocity, the looser twist you can go.
This is why Bill A. chose 1/7.5" twist on the carbine barrels, and 1/9 twist on some of the longer pipes.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
