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Twists and best ammo weight for them

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  • 2 weeks later...

This is from Shilen Barrels 


- 7" * for heavy VLD bullets and/or subsonic ammo.
- 8" for bullets heavier than 220 gr.
- 10" for bullets up to 220 gr.
- 12" for bullets up to 170 gr.
- 13" * Ratchet rifled 4 groove
- 14" * for bullets up to 168gr.
- 15" * for bullets up to 150 gr.
- 17" * for bullets up to 125 gr.


This is from Armalite which uses a 1:10 twist


Your SuperSASS™ is designed to fire all standardized U.S. military 7.62mm NATO cartridges 
and all factory loaded cartridges in .308 Winchester caliber (except cartridges using saboted 
projectiles). Do not attempt to fire any other cartridges in this firearm. 150 grain through 175 
grain projectiles provide a good combination of accuracy and functional reliability, with 168 
grain particularly recommended.



I have always used 168 gr FGMM or Hornady not the TAP and Black Hills out of 1:10 twist regardless if it is a bolt gun or semi-auto .308. Just understand that out of a 20 inch and even a 24 inch barrel  i believe the 168 starts to go subsonic at / around 800 yards. The M118 LR  i.e. 175 hangs in there till 1000 yds  

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Based on that info from Shilen, you'll find a very, very, very few barrels that are cut for 1:11.25 twist.  This is supposedly the optimum twist for a 175gr BTHP Sierra MatchKing projo. 


1:10 twist will run the heavies very, very well. 

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In previous .308s like my old Remy 700 bolt gun I would run what I could find such as 150,156,168 and 180. It did fine with all but the 150s they didn't group as well.  I do agree that the ideal twist on a 20 inch or so is the 1:11 1/4 twist for both the 168 and 175 grain. Rock Creek also makes a 1:11 1/4 twist barrel. The Knight Armament is a 1:11 5 R .

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 I helped a friend of mine who just retired build a DPMS using that barrel. He has yet to shoot it due to some serious surgery how does it shoot?

it shoots better than I do. I'm still jerking around with trying to get scope + sights zeroed, and have just crappy binoculars to use so its not working out all that well. With them not being actually at point of aim in the scope, I was putting out 3 shot groups in the 2 inch range with garbage 145gr south african 1980s mil surplus ammo, so not exactly optimal ammo. I have some 168gr match ammo, but was saving that for once the rifle is broken in and everything at least basically zeroed.

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For the 1-10 twist, you can shoot any weight bullet you want from 125 to 200g bullets. For VLD bullets go to Berger web sight for more info. For the 308 AR I would stick with 155, 168, and 175 MK for cycling of the BCG. The 1-10 will shoot 185 Berger and 190 as well, but would recommend a heavy spring and Hyd-buffer on the rifle and an adjustable gas block to cut down on the gas pressure.  

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Sweet, Sounds like I need to invest in some 168 instead of the 150 I have been shooting then. I finally passed the 200 rd for my barrel, though I dont think I properly broke it in. Just went shooting to shoot, then take it home and clean it really well. I still plan on replacing the stock RRA 20" with a better barrel, any suggestions for that? I like the length of 20" and would prefer to keep it there. I just want this thing shooting out and touching plates at 1000 yds and further.

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I have just been using 150gr simply because it is what I was shooting before and what I found in stock. Also, I was thinking about it, I might go to thw 24" barrel for reaching those hard to get place :P what are the thoughts for bullet weight and barrel twist at that length?

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I would still stick with a 1:10 / 1:11 twist. If I remember correctly say on a 1:10 every 10 inches the bullet and made 1 full 360 degree rotation so on a 20" rotation the bullets has made 2 complete rotations. The 24" inch will be heavy but will give you good accuracy with match grade ammo and give you a little bit extra velocity.  Just remember that too long of a barrel can also give you excessive barrel whip depending on the barrel contour......

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I was thinking a bull barrel maybe for the 24" variation, after all, I will not be carrying it very far. Apparently, just looking at the interwebs, the 150gr .308 Win was actually designed  to be used in a 24" 1:12 barrel...

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Again, from "Hatchers Notebook", just after WW1, one of the rifiloing machines at Springfield Armory "slipped" and was turning out bbls with a 1-11.5" twist.   They shot the std. "ball" ammo better than the 1-10" bbls.

   So, what did the Military do?   Recalled all the bbls, and destroyed them, and went back to 1-10".



   By the way, the origional 1-10" bbls were desinged for 220 grain pills. From the "origional" Kraig-Jorgeson 30-40 rifles.

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I am fine with shooting 150's for the long range fun, but I am thinking 165-168 for my shorter barreled hunting upper. Just from the math that I was able to find online (really wish I had more resources than other blogs) then a 150 gets optimal spin for a 24" barrel grooved at 1:12 and a 165 gets close to optimal spin for a 16" grooved at 1:10. I personally wouldn't mind getting an 1:11.5 grooved 24" barrel because from what I have read on the interwebs (more blogs), that actually did shoot better than the standard 1:12.

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  • 3 months later...

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