9mm Rifling Twist Rate Question

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9mm Rifling Twist Rate Question

Post by Bigtrout on Thu Jan 21, 2016 10:13 am

I know it's a stretch to compare 1911 accuracy with revolver accuracy but here goes.  The Scheumann article online dealing with twist rate for 9mm states a 1:24 twist is probably the optimum for 9mm barrels.   They do not yet produce this twist due to their 1:32 inventory.   My RO has 1:16 stock NM barrel.   My S&W 986 has a 1:10 twist and early indications are it will shoot much tighter groups than the RO.  I realize that comparison is like apples and avocados.  My question is if S&W makes the 929 (6.5" bbl.) and 986 (5") for competitive shooting in 1:10, why do match barrel makers have a 1:32 twist in their barrels?   Most threads I've read claim a faster twist is the kiss of death for 9mm.  Thanks for any insight.

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Re: 9mm Rifling Twist Rate Question

Post by Jon Eulette on Thu Jan 21, 2016 10:47 am

Schuemann barrels are typically for IPSC race guns. They use higher velocity/pressures to make compensators function more efficiently. Most PPC guns are also using higher velocities to get the tight groups. KKM barrels are finicky and require load development. They make 2 different twist rates and lots of people are using 1:32. They are finding (Border Patrol & AMU) that 6" KKM is having gas problems in 6' barrel. Many shooters are switching to Kart 1:16 for 6" pistols. The Kart is more forgiving to load for. The Kart doesn't shoot quite as well at 50 but some trade offs are worth slightly less accuracy. For BE we desire low velocities. The standard 9mm barrel can't do it accurately with low velocities. So faster twist helps. I have been rebarreling several pistols from KKM to Kart recently. I had a shooter shoot personal best last year at PPC nationals with the Kart. I wish I could get one in 1:10 ;p)
Jon

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Re: 9mm Rifling Twist Rate Question

Post by Jerry Keefer on Thu Jan 21, 2016 11:07 am

Jon Eulette wrote:
I wish I could get one in 1:10 ;p)..
Jon
Here's one..Smile
https://youtu.be/R3plYQZNeaI

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Re: 9mm Rifling Twist Rate Question

Post by Jerry Keefer on Thu Jan 21, 2016 11:19 am

What Jon said is correct.. Accuracy games are not the same as the compensated speed games..
It's better to error on the side of faster twist.. I shot my first PPC games in 1980.. The twist rate was overwhelmingly 10 twist in those days.. 10/12 is still the preferred rate of twist for 38/9mm.. I have played with 14 twist 45 wadcutter and hope to try a 12 twist later this spring... The 14 twist 45 shot much better than our standard after market barrels..

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Re: 9mm Rifling Twist Rate Question

Post by Dr.Don on Thu Jan 21, 2016 11:32 am

This thread shows the results of my experimentation with a 12 twist 9mm 1911 last year.  Lot's of replies, long thread, but it produced essentially a 1.5" gun using low velocity 147 XTP's.

http://www.bullseyeforum.net/t3825-1911-9mm-softball-accuracy?highlight=softball


Last edited by Dr.Don on Thu Jan 21, 2016 2:57 pm; edited 1 time in total (Reason for editing : Edited link so it would go to page 1 of the thread.)

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Re: 9mm Rifling Twist Rate Question

Post by Wobbley on Thu Jan 21, 2016 9:02 pm

Your tool needs a chip breaker.   Smile
Jerry Keefer wrote:
Jon Eulette wrote:
I wish I could get one in 1:10 ;p)..
Jon
Here's one..Smile
https://youtu.be/R3plYQZNeaI

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Re: 9mm Rifling Twist Rate Question

Post by james r chapman on Thu Jan 21, 2016 10:30 pm

Nah, looks good to me.

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Re: 9mm Rifling Twist Rate Question

Post by Jerry Keefer on Thu Jan 21, 2016 10:45 pm

Wobbley wrote:Your tool needs a chip breaker.   Smile
Jerry Keefer wrote:
Jon Eulette wrote:
I wish I could get one in 1:10 ;p)..
Jon
Here's one..Smile
https://youtu.be/R3plYQZNeaI
I don't know what the analysis the steel is, but it certainly machines well.. Douglas blank..

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Re: 9mm Rifling Twist Rate Question

Post by Bigtrout on Fri Jan 22, 2016 10:42 am

If I had chips that long coming off my lathe as a toolmaker apprentice my mentor would have chewed my head off.  LOL.

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Re: 9mm Rifling Twist Rate Question

Post by james r chapman on Fri Jan 22, 2016 12:04 pm

A toolmaker apprentice should be grinding his own toolbits.

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Re: 9mm Rifling Twist Rate Question

Post by Bigtrout on Fri Jan 22, 2016 12:31 pm

james r chapman wrote:A toolmaker apprentice should be grinding his own toolbits.
I did but was sometimes too lazy to grind in the chip breaker.   Steel was pretty unforgiving but aluminum barstock would pick you up and drag you into the bed.   I did graduate but immediately got into the engineering department....maybe best for everybody concerned.

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Re: 9mm Rifling Twist Rate Question

Post by rfmiller on Fri Jan 22, 2016 12:33 pm

The new barrels from Apex for the S&W M&P 9mm which claim significant accuracy improvement are 1:10 twist.  Although a lot of the improvement comes from the better "fit" and closer tolerances, I'm sure the twist is significant.

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Re: 9mm Rifling Twist Rate Question

Post by james r chapman on Fri Jan 22, 2016 12:42 pm

I can show nightmare groups from S&w's "perfectly within acceptable standards" m&p barrels.

I dumped mine on a perfectly happy 7 yard shooter who though it the cats ass.


Last edited by james r chapman on Fri Jan 22, 2016 12:43 pm; edited 1 time in total (Reason for editing : added gun type)

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Re: 9mm Rifling Twist Rate Question

Post by rfmiller on Fri Jan 22, 2016 12:54 pm

Yes, those of us who used M&P's in "run and gun" could appreciate it until a precise shot was necessary (although many "7 yard shooters" can't seem to do that with any gun).  I did a lot of work on mine and may try one of these barrels.  Many manufacturers have lax "standards."  This is nothing new.  When I purchased a new K-38 in the early 80's it went straight to the gunsmith the trigger was so bad.  Now I can fix that myself.

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Re: 9mm Rifling Twist Rate Question

Post by Jerry Keefer on Fri Jan 22, 2016 1:57 pm

Bigtrout wrote:
james r chapman wrote:A toolmaker apprentice should be grinding his own toolbits.
I did but was sometimes too lazy to grind in the chip breaker.   Steel was pretty unforgiving but aluminum barstock would pick you up and drag you into the bed.   I did graduate but immediately got into the engineering department....maybe best for everybody concerned.
At first I thought this was a joke..
That is a Kennametal 2 Radius, coated carbide insert with a integral chip breaker. It's set dead center, taking a .015 pass.. It is rated for alloy steel and aluminum. I don't spend/waste time grinding general purpose tools when inserts are readily available and far superior in every way. Threading tools, yes, I grind them out of HS, MO-MAX or REX AAA
I could care less, whether the chip breaks or not..The finish and accuracy out weighs my concern for a broken chip..

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Re: 9mm Rifling Twist Rate Question

Post by james r chapman on Fri Jan 22, 2016 2:12 pm

It wasn't directed to you Jerry, its obviously either a sandvik or kennametal insert doing its proper job.

But, will send you a pint of Wild Turkey if it'll soothe the feathers...lol

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Re: 9mm Rifling Twist Rate Question

Post by spursnguns on Fri Jan 22, 2016 3:58 pm

james r chapman wrote:It wasn't directed to you Jerry, its obviously either a sandvik or kennametal insert doing its proper job.

But, will send you a pint of Wild Turkey if it'll soothe the feathers...lol

James. I'm upset too.  My address will be forthcoming for my Wild Turkey.

Jim

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Re: 9mm Rifling Twist Rate Question

Post by waid1406 on Sun Feb 14, 2016 12:23 pm

I shoot a 1/24 Ray Pulver in my sig sauer X-6 set for PPC. 
Never shoot any more accurate gun in 9x19. 
With the ammotech 123gr FMJ TC bullet it hold 1" at 50y.
A lot of australians shoot the 1/24 in 9x19 and they are super accurate.

The 1/32 is realy picky only working with a 115gr XTp or HAP. The 1/24 eats anything
you give it, from 95gr HP to 147gr FMJ

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Re: 9mm Rifling Twist Rate Question

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