13 twist barrels

W

WallyDog

New member
How many of you are having luck with 13 twist 6mm barrels? PM me if you dont want to go public with your results. They look pretty darn good when you run numbers especially on the longer jackets. Also, what ever happened to moly bullets? Sure was nice to shoot them and not clean every match. Sorry for the old timer questions but Im trying to catch up after being gone a while.

Wallydog
 
I don’t think I ever heard of anybody shooting a 13 twist for SR benchrest, are any out there?
What jacket/ bullet weight are you running numbers on?
 
tim said:
I don’t think I ever heard of anybody shooting a 13 twist for SR benchrest, are any out there?
What jacket/ bullet weight are you running numbers on?
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I'm not wanting to parse this out with 14 twist shooters. I'm interested in 13 twist shooters experiences with .825 jackets.
 
WallyDog said:
I'm not wanting to parse this out with 14 twist shooters. I'm interested in 13 twist shooters experiences with .825 jackets.
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Accuracy suffers little with a 13" twist, and if there was anything wrong with a 13" twist for SR benchrest, then nobody would be experimenting with the 12" and 80 gr. bullets in the 6PPC and the 6mm Grinch. Accuracy suffers a lot if your bullets become unstable from a 14" twist at low altitudes in cooler temps. In Raton we can get away with as slow as a 15" twist.

Michael
 
WallyDog said:
How many of you are having luck with 13 twist 6mm barrels? PM me if you dont want to go public with your results. They look pretty darn good when you run numbers especially on the longer jackets. Also, what ever happened to moly bullets? Sure was nice to shoot them and not clean every match. Sorry for the old timer questions but Im trying to catch up after being gone a while.

Wallydog
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Hi Wally

bullets swaged on .825 jackets runs fine but I turn the question if you want shooting FB or BT since shape of bullets change alot in stability and precision. 13 twist rate should work fine for BT especially with long taper, as 14 twist rate work fine

with FB. Splitting in half you can use a 13.5 twist such as good compromise with all bullets in .825
 
WallyDog said:
How many of you are having luck with 13 twist 6mm barrels? PM me if you dont want to go public with your results. They look pretty darn good when you run numbers especially on the longer jackets. Also, what ever happened to moly bullets? Sure was nice to shoot them and not clean every match. Sorry for the old timer questions but Im trying to catch up after being gone a while.

Wallydog
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I use 13TW with 790 jacket 65 BT bullets. No loss in accuracy that I can tell.
Most of the ranges here are very close to sea level, so maybe that has something to do with it.

Michael
 
Moly coated bullets

If you can't buy any, coat your own. It's a little messy but fairly easy to do with not much cash outlay. In fact, if you're not lazy like I am all you need is a jar and some moly. Might take a week or so but hey...it's cheap. One thing though...be careful how much moly you put in the jar as you might end up with a bigger mess than you wanted to deal with. No harm done but a mess nonetheless.

That said, I don't believe there's any gain at all from moly coated bullets but if you think it helps in any way please coat your bullets.
 
moly bullets

Wilbur said:
If you can't buy any, coat your own. It's a little messy but fairly easy to do with not much cash outlay. In fact, if you're not lazy like I am all you need is a jar and some moly. Might take a week or so but hey...it's cheap. One thing though...be careful how much moly you put in the jar as you might end up with a bigger mess than you wanted to deal with. No harm done but a mess nonetheless.

That said, I don't believe there's any gain at all from moly coated bullets but if you think it helps in any way please coat your bullets.
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I have my own system of moly coating that's really easy and not too messy unless you use too much moly powder. It was all about the cleaning situation as long as it didn't get in the way of accuracy for my way of thinking. The moly that ends up working as a friction reducer/ thermal barrier against eventual heat checking was my interest in it. I worked with coatings of many kinds at one time as a tool and die maker. Some were absolutely amazing and others not so much. Moly had the interesting character of being able to be laid down or removed at will and to be observed with a bore scope as the barrel life progressed. If cleaning between matches were to be reduced or better yet eliminated that in itself could lead to better barrel life and longer accuracy life. Its all about learning and that's why I like BR.
 
Lets do the twist

I believe John Horn has shot 13 twist barrels with some success. You might contact him if he is not plowing the back 40 behind a mule or wrestling coyotes. Tim
 
Thanks

Appreciate the feedback everyone. My thoughts were 68gr boat-tails on .825 jackets were iffy at best with the 14tw. But if they don't work out then I also have about 700 of my own 65 gr FB on .825's left from the old days. Thanks again.
 
WallyDog said:
Appreciate the feedback everyone. My thoughts were 68gr boat-tails on .825 jackets were iffy at best with the 14tw. But if they don't work out then I also have about 700 of my own 65 gr FB on .825's left from the old days. Thanks again.
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Take a look about Berger site about bullets made on .825 jackets and you will have answer
 
ity60107 said:
Take a look about Berger site about bullets made on .825 jackets and you will have answer
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Can you provide a link please? I looked all over the site, even plugged some guesses into the stability calcuprogramulator but didn't find that to which you refer sir
 
Some accurate twist rate calculators!

http://www.jbmballistics.com/cgi-bin/jbmdrag-5.1.cgi

http://www.geoffrey-kolbe.com/barrel_twist.htm

Also, Lilja barrels still offers a free down-load of a program very similar to that of [the late] William (Bill) C. Davis Jr's
Tioga Engineering program.:cool: https://riflebarrels.com/bullet-design/

Any/all of these provide twist rate DATA which you can, "take to the bank". How do I know? I've invested the $ and the time, and proved them (in BR competition), and also via bullet length/weight/twist testing, all the way to less than Sg 1.0. ;) There is no precision penalty at Sg1.5.

One can waltz along the edge, purchasing piles of barrels, looking for that "hummer", or, purchase a barrel/twist which completely damps the yaw & pitch . . . advantage to those who, "dare to be different", and go with Sg 1.5.:eek:

When adhering to the model where a gyroscopic stability factor (Sg) of 1.0 produces a stable (not tumbling) bullet, and Sg 1.5 is desired (nice safety net), with a minimum of Sg 1.4, to damp yaw & pitch, the contemporary MILLER FORMULA calculations rarely correlate with the well proven calculators (above) - I avoid Miller formula calculators, "like the plague". RG
 
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alinwa said:
Can you provide a link please? I looked all over the site, even plugged some guesses into the stability calcuprogramulator but didn't find that to which you refer sir
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In berger site the only calculator is extraction of Miller equation that is not right because don't take care about the shape of any bullets. What i mean is that Berger suggest of bullets made in .825 a twist rate of barrel 13 or faster and only for jackets .790 like the column they can be shoot in 14 twist rate or faster. This is not simply a coincidence ... If you take this information into consideration you will have a simple answers. For better calculation of stability take care of Randy Robinet answer in quote of this topic.
 
You would think with Berger having Bryan Litz as a contractor of some sort, they would have him bring there programs into this century
 
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