Gain twist

[jessej]

#18 02-02-2015, 11:49 AM

Mateo Join Date: Dec 2013 Posts: 904

I've heard great things about the quality Ron Smith puts out. I visited his shop and talked to him for a bit about his gain twist and why he uses to much gain. His response was "decades of experience." Then he went on to say that the gain twist isn't magical it just helps a little bit. And any well made barrel is a well made barrel and will shoot. Be it gain twist or standard. If you haven't heard about his "rebar barrel" I would suggest everyone google it. It's an absolutely brilliant story and the comments left by other shooters are quite entertaining to say the least. I will admit that the "rebar" story was a huge factor into choosing an RKS barrel. I was gonna get a Bartlein but once i found out what Ron could do with "junk steel" I knew he was a master at his trade. Not to mention supporting local and getting to see the shop where my barrel would be made! Cant wait to shoot it. Quote from an Alberta forum

 

[tacomHQ]

Which .460?

.460 steyr? Surely not a .460 wby

Steyr... I heard an incredible story about .460 Weatherby's - brings tears to my eyes both laughing and kick in the n*ts tears of appreciation...

 

[Window]

Actually it seems I read about the gain twist being used by the Germans in WWll. Pretty radical values also.
We have been working with Bartlein on non-standard gains - and to date for great success. Two major reason: first being initial pressure. Screw threads take force. The tighter the thread the greater the force to move an object down the thread. The other reason... maybe later. The minors are a goal of increased velocity, spread the initial pressure pulse over a longer distance, reducing pressure equals less temperature, longer throat life... to name a few.
We built a pair of .460's - identical except for the gain values. One was 1.5tgain the other a 4t gain. The gun with the 4t gain can runs +5gr grains less powder for +70fps on the same round with less felt recoil. Our 300WM runs 12-8 on the twist.. a bit more non-standard features are being added to that barrel and will shortly put rounds down that tube. Accuracy wise the .460's have documented 1.25" three shot groups at 600yds. Perhaps not 6mm territory but recoil control of a 6mm Dasher as compared to a .460 shooting a 635gr Badlands bullet at 3070fps...

That's exactly what I thought would happen but without verification. So why haven't manufactures taken advantage of this on a broader scale? For anyone here with more extensive knowledge, please chime in with any of the negatives.

 

[Weaver93]

Actually it seems I read about the gain twist being used by the Germans in WWll. Pretty radical values also.
We have been working with Bartlein on non-standard gains - and to date for great success. Two major reason: first being initial pressure. Screw threads take force. The tighter the thread the greater the force to move an object down the thread. The other reason... maybe later. The minors are a goal of increased velocity, spread the initial pressure pulse over a longer distance, reducing pressure equals less temperature, longer throat life... to name a few.
We built a pair of .460's - identical except for the gain values. One was 1.5tgain the other a 4t gain. The gun with the 4t gain can runs +5gr grains less powder for +70fps on the same round with less felt recoil. Our 300WM runs 12-8 on the twist.. a bit more non-standard features are being added to that barrel and will shortly put rounds down that tube. Accuracy wise the .460's have documented 1.25" three shot groups at 600yds. Perhaps not 6mm territory but recoil control of a 6mm Dasher as compared to a .460 shooting a 635gr Badlands bullet at 3070fps...

Wasn't gain twist used back in the early 1800s in longrifles? I know there are some guys that compete black powder that still get them from Bobby Hoyt up in PA.

 

[jessej]

Perhaps I might be that guy..LOL.
We are not only looking to reduce overall "whip", harmonics, etc... to reduce the time line of the event. I think we are getting somewhere as we have multiple shooters note that their barrels are flat out the most accurate barrels they have ever had- across a broad spectrum of loads.
Velocity- a constantly evolving pressure event will create a better seal .. arguments coming ... especially in a hostile environment. The other velocity comes from changing directions. When a barrel goes into a sinusoidal whip, the bullet has to change directions. Changing a direction is a loss of speed no matter how small the value is. If I change direction 4-20x within the barrel velocity has to be lost. Even if its only 5fps... or 150fps... We have a shooter who shot a test AB .338 bullet at 300gr at 3450fps with no bolt set back. Now to make the barrel survive that for a few thousand rounds..

Now I feel justified in pursuing my wild ideas.

 

[Petey308]

It might not be worth anything in regards to small arms barrels, but here's a link to a report from an Air Force test that was done with gain twist and sawtooth rifling with the GUA-8 gun in the A-10.

I work these aircraft almost everyday, so it's the first thing I think of when someone mentions gain twist lol.

https://apps.dtic.mil/sti/pdfs/ADB028651.pdf

 

[Old Rooster]

Very interesting.Glad you brought it up jessiej.
I looked up the rebar barrel you mentioned.
Talented guy.https://www.youtube.com/watch?v=8cPjYD59VOA

 

[Mike Matteson]

I looked at this sometime back. Found that most match shooters use single twist rate barrels. So I stayed with a single twist rate barrel. Not that I know much about anything, but my thinking was: coming out of the chamber into the lands it would be easier and less pressure. Gain the twist rate as it goes down the tube for the type of bullet used. Meet the twist required or needed, What velocities was I going to achieve, and could I use heavier powder loads, because of less pressure at the start. The other question is what is a saw tooth rifling?

 

[jessej]

The other question is what is a saw tooth rifling?

My exact thoughts

 

[Sheldon Root]

Now I feel justified in pursuing my wild ideas.

I have a custom in 257 Wby Mag. Barrel was by RKS. Gain is very near 1:16 at start and goes to 1:7.5. Special for
a 115 grn Barnes or Hornady 117. right out of the box used two rounds to sight in scope and then 3 for grouping.
3/8" at 100 yds. Velocity at 3750 but dropped it back around 3200 to save on powder and barrel wear. The idea behind the gain is to give the bullet a bit of chance to move before the hard twist at the muzzle. Lessons the
recoil a bit so pressure is lower on initial powder ignition and movement of the bullet. Have a bore scope and have not seen any abnormal marks. Don't be afraid to try one , they work very well. SR

 

[Weaver93]

I looked at this sometime back. Found that most match shooters use single twist rate barrels. So I stayed with a single twist rate barrel. Not that I know much about anything, but my thinking was: coming out of the chamber into the lands it would be easier and less pressure. Gain the twist rate as it goes down the tube for the type of bullet used. Meet the twist required or needed, What velocities was I going to achieve, and could I use heavier powder loads, because of less pressure at the start. The other question is what is a saw tooth rifling?

Six groove sawtooth rifling: The rifles of A.B. Reading and Brother

Mentioned earlier, this piece on the Five Forks battlefield is interesting for several reasons. Before the normal “walk around,” a bit about A.B. Reading & Brother. Vicksburg, Missi…

markerhunter.wordpress.com

I think it is called ratchet rifling too.