AR15.Com Archives
 9mm Twist rate
usmcgunman  [Member]
1/29/2012 11:44:33 AM EST
Building my first 9mm and getting ready to buy the barrel. I have found a few different twist rates for the 9mm from 1:10, 1:15 and 1:14. So what is the best rate to get for overall shooting and accuracy? When I say overall I mean most bullet weights. This will be just a toy and mostly a plinker to have fun at the range with. Thanks for all the help!
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osprey21  [Life Member]
1/29/2012 12:01:06 PM EST
My Uzi barrel has a 1:10 twist and itr shoots everything well, as does my Colt 1:10 barrel, that's good enough for me.

YMMV
usmcgunman  [Member]
1/30/2012 3:39:35 PM EST
No one else has any imput?
kaotic504  [Member]
1/30/2012 6:17:02 PM EST
well i think most pistol are between 1:10 to 1:16. my TROS barrel is 1:10, while the Noveske i have coming in is a 1:12. basically i'll only be able to give you feedback once i get my Noveske in and check for accuracy. i know when i sighted my Tros 5" barrel in, it was within 1 inch at 25yrds w/ my EOTech. i'll probably try to take it out to 50yrds with some magnification and see how it does there, and then compare it to the Noveske and their polygonal bore. I really wanted to be able to shoot it w/ 115gr ammo well, and 147gr subsonics. I will have to report back once I am able to test it. Hopefully, i'll have my barrel tomorrow but I don't know if i'll be able to test this weekend.
forever4  [Team Member]
1/30/2012 6:48:53 PM EST
I can not tell you which twist rate is best. There are several and there are more opinions on this than there are clear answers. Rock River and CMMG use a 1-10 on their 9mm carbines. Oly uses 1-16 twist, while Yankee Hill does a 1-14. Interesting that the MP5, one of the most widely used and best respected 9mm Sub Guns uses the 1-10. The majority of my 9mm carbines are 1-10 but that is not by my choice, its just the way they were made. Yet, if you look at serious competition guns that have to shoot their best the high end shooters use a 1-16 or even a 1-20 to get max accuracy.

So, this is why you may not get a lot of definitive responses, no one can agree!
maleante  [Team Member]
1/30/2012 9:40:20 PM EST
Model 1 sales sells their 9mm barrels in 1/15. I had one a long time ago that shot fine.

Colt is 1/10. Colt is also the first company to design and sell the 9mm AR. I only use Colt barrels now. They are great barrels that can not be matched quality wise.

About twist rates though, honestly 1/10, 1/12, 1/14, 1/15, 1/16, 1/20 who knows which is truly "the best", they all do what they are supposed to...




FWIW, the faster rate (1/10) supposedly helps stabilize heavier bullets.
GHPorter  [Team Member]
1/31/2012 1:45:33 AM EST
The most common twist rate is 1:250mm (almost identical to 1:10") right hand twist. Different barrel makers sometimes have different numbers of grooves (I seem to recall my S&W M559 has 5 grooves/lands), but for pistol barrels, the twist rate is pretty much standard at 1:10".

Some carbine barrels are made with slower twists, but their utility is debatable. Both my factory RRA 16" carbine barrel and my Spikes 10.5" SBR barrel have a 1:10 twist and are more accurate than I am.
kevins_garage  [Member]
1/31/2012 5:12:42 AM EST
Schuemann, Nowlin, Kart, and others spec 1/15 or 1/16 for their comp/match 9mm barrels and some even offer as slow as 1/24-1/32???

Some say 1/10 is way to fast of a twist for 9mm????

Some say 1/20 is the optimal twist for 9mm????

I have read that the Beretta M9 National Match pistols used at Perry have 1/32 twist KKM or BarSto barrels...

I won't speculate on why 1/10 is most common, but some think it is just a carryover from the old luger days and an artifact of rounding from a metric twist of just under 1/10 (and if Glock, Sig, and HK use 1/10, it must be optimal, right?). When it comes to 9mm AR barrels though, you are pretty much going to be stuck with 1/10 or 1/15 unless you want to pay more for a custom twist. Either 1/10 or 1/15 will shoot pretty much all factory ammo just fine - try different ammo to see which is most accurate in your barrel. If you reload, just develop the most accurate load for your barrel and don't worry about the twist.
usmcgunman  [Member]
1/31/2012 8:10:13 PM EST
Thanks for all the info!
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