Gain twist
- Thread starter Nukes
- Start date
I've been really curious about this too. I can't even find anyone who will explain theoretical benefits.
I posed this question to several of my engineer friends. 1 chemical, 1 mechanical, and 1 civil.
"How much, if any benefit would there be to using a gain twist barrel?" In the situation I gave them there were 2 barrels a standard 1-11 and a 1-16 to 1-11 gain twist.
The factors were determined to be:
-How much force is applied at 1-16?
-How much force is applied at 1-11?
-What are the effects of said forces on ballistics, barrel, and projectile?
The theoretical determination was that whatever the benefit of reducing the force would be marginal. Both the barrel and the projectile are designed to withstand these forces. Both the barrel and the projectile are consumable. A 5 or even 10% reduction in wear (although none of them believed the reduction would be > than 1 or 2%) does not relate to a substantial gain in barrel life. Minor changes on internal ballistics can have significant effects (both good and bad) on external and terminal ballistics
Alas, this is all just thought exercise, and none of them have substantial firearms experience. At the end of the day it came down to Cost Benefit Analysis.
As one friend put it, "If there were substantial benefits the companies would have third-party scientist verify their claims."
"How much, if any benefit would there be to using a gain twist barrel?" In the situation I gave them there were 2 barrels a standard 1-11 and a 1-16 to 1-11 gain twist.
The factors were determined to be:
-How much force is applied at 1-16?
-How much force is applied at 1-11?
-What are the effects of said forces on ballistics, barrel, and projectile?
The theoretical determination was that whatever the benefit of reducing the force would be marginal. Both the barrel and the projectile are designed to withstand these forces. Both the barrel and the projectile are consumable. A 5 or even 10% reduction in wear (although none of them believed the reduction would be > than 1 or 2%) does not relate to a substantial gain in barrel life. Minor changes on internal ballistics can have significant effects (both good and bad) on external and terminal ballistics
Alas, this is all just thought exercise, and none of them have substantial firearms experience. At the end of the day it came down to Cost Benefit Analysis.
As one friend put it, "If there were substantial benefits the companies would have third-party scientist verify their claims."
I remember Lilja had a blurb about this on their site at one time. Being a button rifling shop it is easy for them to play with twists. To paraphrase what they said, gain twist works, constant twist works, loss twist does not work. They speculated that the key was the projectile needed to be held to the same side of the lands the whole trip through and that they shifted in the loss twist resulting in inconsistency. Anyhow, the take away was gain twist didn't gain you anything but worked fine.
A few years back I tried to discuss gain twist w/engeneers @ FN in Cola. SC . They seemed kind of tight lipped ,didn't know how to take it. Paul
Gain twist are thought to be easer on bullets because they start the bullet rotating slower initially and increase as the bullet passes
down the barrel To reach the best twist rate for the heavier bullets. With ever more velocity and heaver bullets starting a bullet rotating
in a fast twist can separate the jacket from the bullet core. (Most Big bores like the 416s and larger use slow twist for 400+ grain bullets
and normally 8 lands to prevent the jacket from shedding).
In theory it should be great but the engraving on the bullet leaves something to be desired and any benefit of the gain twist is lost, and
with the better bullets we have today this is not a problem with the ultra high velocity cartridges of today.
As someone else stated, if it was better all barrel makers would offer there barrels in a gain twist configuration. It is not hard for them to
do there is just no advantage to gain twist at this time.
J E CUSTOM
down the barrel To reach the best twist rate for the heavier bullets. With ever more velocity and heaver bullets starting a bullet rotating
in a fast twist can separate the jacket from the bullet core. (Most Big bores like the 416s and larger use slow twist for 400+ grain bullets
and normally 8 lands to prevent the jacket from shedding).
In theory it should be great but the engraving on the bullet leaves something to be desired and any benefit of the gain twist is lost, and
with the better bullets we have today this is not a problem with the ultra high velocity cartridges of today.
As someone else stated, if it was better all barrel makers would offer there barrels in a gain twist configuration. It is not hard for them to
do there is just no advantage to gain twist at this time.
J E CUSTOM
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You guys haven't been paying attention.
Bartlein is doing a lot of gain twist barrels, or at least more and more of them.
The Bravo 6 Delta from GAP along with several Team GAP rifles are gain twist. 1-7.7 to 8.5 twist.
My 338 Norma Magnum used to test the new ZA monolithic solids is a gain twist, 1-13 to 5.4 this is a bit aggressive but it works in this particular application.
Because Bartlein has modern machines they are able to do it better and are finding small gains have great results like with the GAP 6mm Creedmoor rifles.
I believe George also has an F Class 308 in a gain twist.
Modern methods, computer controls, and a better understanding is moving this forward. I foresee more gain twist offerings coming out of Bartlein in the future, they hit on the formula where others failed.
Bartlein is doing a lot of gain twist barrels, or at least more and more of them.
The Bravo 6 Delta from GAP along with several Team GAP rifles are gain twist. 1-7.7 to 8.5 twist.
My 338 Norma Magnum used to test the new ZA monolithic solids is a gain twist, 1-13 to 5.4 this is a bit aggressive but it works in this particular application.
Because Bartlein has modern machines they are able to do it better and are finding small gains have great results like with the GAP 6mm Creedmoor rifles.
I believe George also has an F Class 308 in a gain twist.
Modern methods, computer controls, and a better understanding is moving this forward. I foresee more gain twist offerings coming out of Bartlein in the future, they hit on the formula where others failed.
It's a fad that comes and goes in cycles, been doing so for the last 50 years. If it were any better than a constant twist then all the benchrest shooters would be using it, but they're not. That should tell you all you need to know about it.
I agree with Lowlight. Although I do not have personal experience with gain twist rifling, I leverage my opinion by the property of friction. Projectiles traveling through barrels with slower twist rates have less contact with the lands (in terms of time). For example, if we straightened the lands in two, 20in barrels in .308 ID: one 1:5 twist and another 1:10 twist, we would see that the 1:10 twist barrel has 20.0934” of contact with the projectile, while the 1:5 twist barrel has 20.3712” of contact. Therefore, barrels with shallower twist rates impose less friction on projectiles per given length barrel. I speculate that less friction would increase projectile velocity for a given load. The same conclusions may be implied to gain twist rifling (I.e. less friction). The degree to which this affects velocity may be slight, but any benefit is still an advantage. I also believe angular acceleration plays into this, but I don’t know the formulas to calculate that now.
For some frame of reference, 6mmBR.com has published velocity differences up to 80fps in 1:10 to 1:12 twist barrels for identical loads with 80-90gr projectiles (although reloading components nor cartridge are listed, the difference in velocity presents some factor of velocity increase).
Since bullet acceleration in the barrel is logarithmic, gain twist has to work if properly matched to burn-rate and bullet bearing surface; I guess you get the speed of the slow twist and stabilization of fast twist. Kinda cool.
If I'm not mistaken, Rock Creek was using gain twist in all of their barrels, albeit a minor amount. As for personal experience, I know my Rocks shoot better than any others I have run ,but thats only a few others, as I stuck to rock after the first one shot so well. Next closest I've had accuracy wise was a 30cal. Hart and it was just a standard 10 twist button barrel. I'm curious to see the results when someone can actually quantify a difference beyond anecdotal observation.
I definitely agree that there is theoretical advantage. However, I prefer empirical evidence. This all phenomenon, and I see no reason that this cannot be tested using the scientific method.
+1
This has been tried and tried again and is still not the new standard for rifle barrels.
It is also not a new idea. at the turn of the century the Germans tried it and again in the second world war they took another run at it
In the really big guns (Like the Paris gun) because of the size and weight of the projectile and the desired accuracy. They opted for more
lands and groove's with a uniform twist.
Gain twist barrels are just as easy to manufacture as standard twist barrels, and with todays demand on accurate barrels if it was better
all would be making them. Most of them will make a gain twist barrel for you if you special order it.
After talking to several of the best barrel makers about gain twist they recommended the same thing experience has shone me. More grooves/lands
that don't upset as much jacket material during engraving and the slowest twist you can get by with. (Bench rest normally shoot a slower twist
than normal). Shallow groves and lands with 6 or 8 grooves.
I like the 3 groove barrel for ultra fast bullets (4000 ft/sec+) but they are hard on bullets because of there width and the amount of upsetting
done to the jacket and only the best bullets will hold up under these velocities.
Some day maybe someone will perfect the gain twist and it will be the new standard for accurate rifles, But for now, I for one will go with the
barrel makers recommendations If I expect sub 1/4 MOA accuracy.
Just my opinion and experiences
J E CUSTOM
S&W uses gain twist in their 460 mag. pistol . Don't remember spacifics-seems like it started @ 1/100 not really sure where it ended. Seems like gain twist would be like a wood screw w/different rates of threading, it would be damaging to the wood being the softer material, ie. hard on the bullet guilding metal being the softer material,especially with severe rifling rate changes. Wouldn't this mess up the rifling engraving on the projectile (particularly the longer ones)?Would it in extreme cases cause bullet instability especially on longer bullets at longer ranges where you would hope to see improvements from additional bullet velocity and rotational speed ? Paul
I don't really see the advantage to gain twist when you're only changing the twist rate slightly. Going from 7.7 to 8.5 twist seems insignificant. I can understand the setup in the US 20mm vulcan barrels where they are taking a cartridge with a 62K psi chamber pressure and starting the rifling at nearly straight then ramping up to a fairly high twist rate over a 5.5 ft barrel length. It allows the ability to avoid upping the chamber pressure and permits the thinner and lighter barrel to be used as that is important in an aircraft especially when there are 6 barrels rotating at 4000rpm. The 20 and 30mm projos are also frequently spin armed high explosive so the spin rate is important for that reason as well. We aren't shooting any spin armed bullets and our barrels are heavy enough that going from a 1-10 to a 1-8 twist rate won't bump the pressure up enough to make much difference. What is the real advantage to gain twist in target shooting??? I don't understand this one.
Frank
Frank
Barrel making machines have not changed for the most part in 75 years. Your average barrel maker is doing it on an old WWII piece of equipment, except Bartlein that has modernized the way they make barrels.
Also thanks to computers, they can understand what is needed better, the fact you don't have to get aggressive in the gain, that a subtle approach is a better approach.
You can say it's old, you can say it's a fad, but you can't say it's been done like it is now. From guys like Noel making a new bullet and pairing it with a Gain Twist to Bartlein finding subtle works.. .it's a new era.
Making a correct gain twist on an old barrel making machine is not the same as making a correct gain twist in a new computer controlled machine. Big difference, and when you consider Krieger's top Benchrest barrel maker is now at Bartlein, you might see the bench rest world follow him and what is going on in that shop.
It may not be for everyone, but it is out there and working and you don't even know it. GAP is just one that been pushing it with Bartlein barrels, the FN Ballista had a Gain Twist Barrel, and there are others... it's just not a "Marketing" point, it's just there.
Also thanks to computers, they can understand what is needed better, the fact you don't have to get aggressive in the gain, that a subtle approach is a better approach.
You can say it's old, you can say it's a fad, but you can't say it's been done like it is now. From guys like Noel making a new bullet and pairing it with a Gain Twist to Bartlein finding subtle works.. .it's a new era.
Making a correct gain twist on an old barrel making machine is not the same as making a correct gain twist in a new computer controlled machine. Big difference, and when you consider Krieger's top Benchrest barrel maker is now at Bartlein, you might see the bench rest world follow him and what is going on in that shop.
It may not be for everyone, but it is out there and working and you don't even know it. GAP is just one that been pushing it with Bartlein barrels, the FN Ballista had a Gain Twist Barrel, and there are others... it's just not a "Marketing" point, it's just there.
For relatively low pressure rounds, with moderate twist rates and typical weights for bore diameter (say a 178 grain .30 caliber at 2650 fps and a 1:10 twist), there probably is not a significant difference. This "group" would encompass most shooting including high-power, benchrest, etc. However, if the bullet we want to push can maintain higher rpm, it can pass through transonic with less disruption (that IS good). Also, there is some testing with bullets getting closer and closer to Sears-Haack body shapes which also benefit from higher rpms. Open tip and a rebated base for instance. The Sears-Haack shapes, under torque, deform and produce less accuracy as a result. While there is some actual benefit in throat erosion due to gain twist, it does not result in any fiscal benefit. Where the benefit comes is in a reduced pressure spike at the time the bullet engages the lands. If you look at a free-body force diagram of a bullet at the snapshot in time it engages the lands, it is clear that eliminating, or reducing the torque will result in less deformation of the jacket and at the jacket to core interface. Now, think about solids. I pulled some Barnes solids out of gel, sectioned them did metallurgical mounts. Under very high magnification, I was able to see rupture in the grain structure that I attributed to torque.
So let me sum it up...Gain twist, for the majority of the shots taken, has no real measurable benefit. However, when the distances are stretched, there certainly can be benefit, especially in certain circumstances. Long solids, higher pressures, heavy for bore projectiles, there certainly is benefit.
So let me sum it up...Gain twist, for the majority of the shots taken, has no real measurable benefit. However, when the distances are stretched, there certainly can be benefit, especially in certain circumstances. Long solids, higher pressures, heavy for bore projectiles, there certainly is benefit.
I have no personal experience with gain twist, but some cursory research points out these items yet to be mentioned:
- gain twist was used well before the civil war to stabilize lead rifle bullets and then mini-balls. Today, one can still buy premium black powder barrels with gain twist if you are looking for some extra accuracy. One reason this is done is that black powder charges burn long, often even after the bullet has left the barrel. Which leads to...
- Longer burning powder charges in loads benefit from gain twist by evening out the pressure curve (internal ballistics). This has been known for a long time, but...
- Manufacturing a gain twist barrel prior to recent advancements in CNC machines and technology was always a more expensive process... Which is the answer to the question asked earlier; "why doesn't every manufacturer already make their barrels with gain twist?". Plus it's somewhat application specific. Which leads to...
- Every day off-the-shelf rifles must be able to shoot acceptably with just about any factory load, with the largest use for casual hunting (probably the largest segment of the rifle purchasing public - I don't have the stats). Gain twist (at least and especially in the past), tends to be designed around a specific application and sometimes even a specific load combination as that is where the most benefit is achieved.
So there you have it. Some basic information gleaned from a few pretty reliable sources and available with a couple specific searches, not from forum threads and personal blogs.
Sometimes, what is old does truly become what is new; when newer techniques, knowledge and applications are realized.
- gain twist was used well before the civil war to stabilize lead rifle bullets and then mini-balls. Today, one can still buy premium black powder barrels with gain twist if you are looking for some extra accuracy. One reason this is done is that black powder charges burn long, often even after the bullet has left the barrel. Which leads to...
- Longer burning powder charges in loads benefit from gain twist by evening out the pressure curve (internal ballistics). This has been known for a long time, but...
- Manufacturing a gain twist barrel prior to recent advancements in CNC machines and technology was always a more expensive process... Which is the answer to the question asked earlier; "why doesn't every manufacturer already make their barrels with gain twist?". Plus it's somewhat application specific. Which leads to...
- Every day off-the-shelf rifles must be able to shoot acceptably with just about any factory load, with the largest use for casual hunting (probably the largest segment of the rifle purchasing public - I don't have the stats). Gain twist (at least and especially in the past), tends to be designed around a specific application and sometimes even a specific load combination as that is where the most benefit is achieved.
So there you have it. Some basic information gleaned from a few pretty reliable sources and available with a couple specific searches, not from forum threads and personal blogs.
Sometimes, what is old does truly become what is new; when newer techniques, knowledge and applications are realized.
Some of the best short range benchrest shooters have been using it succesfully for awhile as well. Major shoots have been won around the world more than once with gain twist. If gain twist doesn't help it sure doesn't hurt.
I've gotten 1850 rounds this last year and a half through my bartlien gain twist. starts at 10 twist and ends at 8.2. Very accurate rifle to say the least. I have been impressed with everything about the bbl fouling, cleaning, shooting, speed, everything. Its a 19" 6.5 creedmoor that is crazy accurate. It was never broken in, cleaned for the first time at 1000 rounds, cleaned at 1750 and I have shot about 100 rounds since then. Clean cold bore was dead on. Rifle is built by GAP and its a PSS sender contour that's fluted and I have shot nothing but factory ammo through it. I have shot it out to 1330 yds a few times with great results knowing the cartridges limitations with the bbl length. It is at GAP again now being fitted for another so when the bbl does go out I will have 2 more ready to roll. That and a EFR rail for my PVS 22, Figured I'd do em all at the same time.
Well I'll add some information for all. Some of it will be my personal opinion, and I will quote some others on information I have received and will even quote Harry Pope of Pope Barrel fame.....
Gain twist barrels have been around for years....at least the early 1800's and I'm positive it goes back before that....who actually was the first I cannot say. Our 20mm and I believe our 30mm cannon barrels that our military uses are all gain twist type barrels. I know the 20mm's are for sure. I've got the drawings for those.
The master barrel makers from the late 1800's to early 1900's all made gain twist barrels for the match rifles of the day. These would have been the Schutzenfest type rifles. The great single shots like the Ballards, HI Walls, Stevens 44 series etc....Pope I believe gave his credit for learning barrel making from Schalk. Schalk, Pope, Zischang, Schoyen all made gain twist type barrels and most likely straight twist barrels. Pope was most likely the most well known and probably made the most of them. You have to remember that that the match rifles of back then all shot lead bullets. Guys who shoot Schutzenfest type rifles now a days and if you have a rifle with Pope barrel on it that is in good shape guys are still winning with them. A Pope barreled rifle (either on a Ballard or Hi wall action) actually held the 200 yard bench rest record for a 10 shot group that was fired in the early 1900's up to I believe it was the 50's or real early 60's. This group for cast lead bullets and a cartridge gun I'm pretty sure is still the official record holder as well. I believe a guy by the name of Rowland shot it. I'd have to look it up again. I will quote Pope on what the benefits were of the gain twist barrels....remember this is for lead bullets.
1.) The twist being less at the breech, gives less friction to the bullet; it there fore starts easier and quicker, giving the powder less time to burn on in front of the chamber, which there for fouls less than in a barrel of uniform twist at the same necessary muzzle pitch (twist).
2.) The slight change in angle of the rifling, in connection with the choke bore (lapping choke into the bore of the barrel), effectually shuts off any gas escape of gas and prevents gas cutting, which is another case of imperfect delivery.
3.) It holds the muzzle loaded bullet in position much better than a uniform twist barrel.
I have a Ballard Rigby 6 1/2 off hand rifle. It was rebarreled at the Stevens factory in the early 1900's. The barrel is marked Stevens - Pope. The gun was converted to .22RF. The rifling is gain twist, left hand twist and 8 groove. The gain twist starts at 1-18 and ends at 1-16.5 at the muzzle. This rifle was just shot and tested after some repair work was done to it by Steve Garbe (SPG Lube/Wyoming Armory) and with Federal Ultra Match ammo (UM1) it was averaging a flat .300" groups at 65 yards. The bore of the barrel is in excellent condition and it's around 105 years old and the rifle itself is around 130 years old. It would be a tough gun to beat in a bench match for a .22cal. rifle. Even with the new rifles that are made now a days.
We all know that a barrel with a uniform twist or a slight gain is the best. A barrel with a non uniform twist will have accuracy issues. No way around it.
I think some of Popes claims apply to jacketed bullets as well. We have one customer who is a former Army (reserve?) Team armorer. They've been fighting pushing the 90gr. bullets out of AR15 rifles at a given velocity and keeping the bullets together and getting accuracy as well. The guy has tested a lot of different rifling, bore size and twist combinations and what he has settled on for the gain twist is a barrel that starts out a 1-13 and ends at 1-6.5. I won't give the rest of his specs. out as far as number of grooves and bore and groove sizes as I didn't ask his permission to do so. We just shipped to him another batch of 20 barrels or so about a month ago. The guys is extremely happy. He is making the velocity with out being over pressure and are not having bullet failure problems.
We have another customer who is ordering .375cal. barrels. Again the twist is starting out 1-16 and ending at 1-8. They are shooting the solid machined copper/brass type bullets. I believe the chamber is .375 Cheytec. We're making another dozen or so barrels for him. I asked him how they are shooting. He said only have been able to shoot out to 1400 yards but his gun has been a .5moa rifle. So they got to be working if they are buying more.
How the gain twist rifling started with us was because Tony Boyer (famed short range bench shooter) called us and asked if we could make them. We said yes. He said one of the best barrels he ever had was a button barrel but when they checked that barrel the twist started out at 14.25 and ended at 1-15. Knowing full well it wouldn't shoot because the twist go slower they decided to try and but flipped the barrel around so the twist started out at 1-15 and ended at 1-14.25. So we made him some barrels and the rest is history with that. Most of the top bench shooters are getting gain twist barrels. Most are around 1-14 to 13.75 twist or a 13.85 to 13.75 twist range. Not a lot of gain just something so the bullet cannot go to sleep in the barrel. The rifling is always putting a fresh bite on the bullet as it goes down the bore.
There are some F-Class and FTR shooters using gain twist but I would say the straight twist are still dominant here.
Is it the answer for everyone? I'm gonna say no but it definitely doesn't seem to be hurting anyone either and in some cases it seems to be helping.
Gotta go for now.....
Later, Frank
Bartlein Barrels
Gain twist barrels have been around for years....at least the early 1800's and I'm positive it goes back before that....who actually was the first I cannot say. Our 20mm and I believe our 30mm cannon barrels that our military uses are all gain twist type barrels. I know the 20mm's are for sure. I've got the drawings for those.
The master barrel makers from the late 1800's to early 1900's all made gain twist barrels for the match rifles of the day. These would have been the Schutzenfest type rifles. The great single shots like the Ballards, HI Walls, Stevens 44 series etc....Pope I believe gave his credit for learning barrel making from Schalk. Schalk, Pope, Zischang, Schoyen all made gain twist type barrels and most likely straight twist barrels. Pope was most likely the most well known and probably made the most of them. You have to remember that that the match rifles of back then all shot lead bullets. Guys who shoot Schutzenfest type rifles now a days and if you have a rifle with Pope barrel on it that is in good shape guys are still winning with them. A Pope barreled rifle (either on a Ballard or Hi wall action) actually held the 200 yard bench rest record for a 10 shot group that was fired in the early 1900's up to I believe it was the 50's or real early 60's. This group for cast lead bullets and a cartridge gun I'm pretty sure is still the official record holder as well. I believe a guy by the name of Rowland shot it. I'd have to look it up again. I will quote Pope on what the benefits were of the gain twist barrels....remember this is for lead bullets.
1.) The twist being less at the breech, gives less friction to the bullet; it there fore starts easier and quicker, giving the powder less time to burn on in front of the chamber, which there for fouls less than in a barrel of uniform twist at the same necessary muzzle pitch (twist).
2.) The slight change in angle of the rifling, in connection with the choke bore (lapping choke into the bore of the barrel), effectually shuts off any gas escape of gas and prevents gas cutting, which is another case of imperfect delivery.
3.) It holds the muzzle loaded bullet in position much better than a uniform twist barrel.
I have a Ballard Rigby 6 1/2 off hand rifle. It was rebarreled at the Stevens factory in the early 1900's. The barrel is marked Stevens - Pope. The gun was converted to .22RF. The rifling is gain twist, left hand twist and 8 groove. The gain twist starts at 1-18 and ends at 1-16.5 at the muzzle. This rifle was just shot and tested after some repair work was done to it by Steve Garbe (SPG Lube/Wyoming Armory) and with Federal Ultra Match ammo (UM1) it was averaging a flat .300" groups at 65 yards. The bore of the barrel is in excellent condition and it's around 105 years old and the rifle itself is around 130 years old. It would be a tough gun to beat in a bench match for a .22cal. rifle. Even with the new rifles that are made now a days.
We all know that a barrel with a uniform twist or a slight gain is the best. A barrel with a non uniform twist will have accuracy issues. No way around it.
I think some of Popes claims apply to jacketed bullets as well. We have one customer who is a former Army (reserve?) Team armorer. They've been fighting pushing the 90gr. bullets out of AR15 rifles at a given velocity and keeping the bullets together and getting accuracy as well. The guy has tested a lot of different rifling, bore size and twist combinations and what he has settled on for the gain twist is a barrel that starts out a 1-13 and ends at 1-6.5. I won't give the rest of his specs. out as far as number of grooves and bore and groove sizes as I didn't ask his permission to do so. We just shipped to him another batch of 20 barrels or so about a month ago. The guys is extremely happy. He is making the velocity with out being over pressure and are not having bullet failure problems.
We have another customer who is ordering .375cal. barrels. Again the twist is starting out 1-16 and ending at 1-8. They are shooting the solid machined copper/brass type bullets. I believe the chamber is .375 Cheytec. We're making another dozen or so barrels for him. I asked him how they are shooting. He said only have been able to shoot out to 1400 yards but his gun has been a .5moa rifle. So they got to be working if they are buying more.
How the gain twist rifling started with us was because Tony Boyer (famed short range bench shooter) called us and asked if we could make them. We said yes. He said one of the best barrels he ever had was a button barrel but when they checked that barrel the twist started out at 14.25 and ended at 1-15. Knowing full well it wouldn't shoot because the twist go slower they decided to try and but flipped the barrel around so the twist started out at 1-15 and ended at 1-14.25. So we made him some barrels and the rest is history with that. Most of the top bench shooters are getting gain twist barrels. Most are around 1-14 to 13.75 twist or a 13.85 to 13.75 twist range. Not a lot of gain just something so the bullet cannot go to sleep in the barrel. The rifling is always putting a fresh bite on the bullet as it goes down the bore.
There are some F-Class and FTR shooters using gain twist but I would say the straight twist are still dominant here.
Is it the answer for everyone? I'm gonna say no but it definitely doesn't seem to be hurting anyone either and in some cases it seems to be helping.
Gotta go for now.....
Later, Frank
Bartlein Barrels
Has Bartlein, or anyone else for that matter, done actual scientific studies with gain twist barrels to determine the actual effects of gaining twist vs standard twist?
I'm sure McDonald Douglas has data to support progressive twist in the bushmaster, and I'm also sure that we will never see it.
I'm sure McDonald Douglas has data to support progressive twist in the bushmaster, and I'm also sure that we will never see it.
Wilwith1l, Other than what I can relay from customers like the AR15 barrels etc....and feed back we've received on them, I'm gonna say no. Like those AR15 barrels they are able to keep the pressures down to the point that the guns seem to be safe and they are hitting the velocities that they are looking for. This is helping against the bullet failure and they are getting the accuracy that they need on top of it. They couldn't do it with any of the straight twist barrels that they received from any manufacturer.
A few of us here do have some gain twist barrels on guns and are shooting them and all I can say is we have no complaints on how they shoot either.
Only the gov't has that kinda time and $$$ to do extensive testing. In order to go a good scientific data test I would say you have to do at least 2-3 barrels at a time. Make all the barrels the same but only change one thing at a time. Like changing the bore size or groove size or the twist etc....and when you run the tests you have to shoot all the barrels at the same time in the same conditions to get any good reliable data out of the tests.
One gov't agency that we make test barrels for is conducting tests right now on different chambers for a certain caliber. They are using the same twist and rifling profile but just changing the chamber specs. for the throat etc...as they are testing new bullets and they are finding that certain chambers/throat specs. are changing the way the ammo shoots. In some cases better and in some not so good. Again they have the equipment, time and money to do testing like that. The average guy/company does not.
We have another customer who did testing (.308win. chambered barrels). They bought gain twist barrels, left hand twist barrels. twist of 1-10, 1-11, 1-12 or 1-9 etc....I was told they will be publishing the data (when I don't know) but I guess you will have to buy the book when it comes out. They won't publicly publish the data on any forum or website. Can't say I blame them. They're paying for it all and it would be one way to recoup some of the costs at least.
Later, Frank
Bartlein Barrels
I had a 260 Rem Improved barrel (Bartlein or Benchmark...can't remember now) with a gain twist. They called it their "T" twist for "transitional." It was something mild, like 9 or 8.5 to 8 twist. Kevin Rayhill suggested I give it a try. It was on my F-class/LV 600 IBS rig a few years ago. Shot very well, but not phenomenally better than any of the other top end barrel manufacturers I've used. Went back to Krieger when I needed a new barrel, because Kevin had 2 of those on hand when I needed one.
I usually get 1900-2200 rounds through the barrel before I have the chamber chopped and re-chambered. Usually can get another 12-1500 rounds before it gives up the ghost for good. 260AI is pretty rough on throats when driven hard and shot rapidly. The gain twist didn't go further (round count), shoot dramatically faster, clean easier, or magically find the X more frequently than any other good barrel I've used. Lija, Shilen, Bartlein, Krieger, Pac-Nor, Benchmark, etc. have all worked for me...never got a truly "bad" barrel yet. Prefer cut rifling, but button rifling has worked just fine for me so far as well.
I wouldn't have a problem buying another gain twist barrel again, but I didn't see enough of a benefit to specifically search for another one either. Granted, the sample size has been extremely small so far. Most of the time I've found there is an accuracy node that is easily achievable with either rifling type, so the claimed velocity advantage is a moot point to me. If there was some empirical evidence showing one was better then the other...we would all be using it.
I usually get 1900-2200 rounds through the barrel before I have the chamber chopped and re-chambered. Usually can get another 12-1500 rounds before it gives up the ghost for good. 260AI is pretty rough on throats when driven hard and shot rapidly. The gain twist didn't go further (round count), shoot dramatically faster, clean easier, or magically find the X more frequently than any other good barrel I've used. Lija, Shilen, Bartlein, Krieger, Pac-Nor, Benchmark, etc. have all worked for me...never got a truly "bad" barrel yet. Prefer cut rifling, but button rifling has worked just fine for me so far as well.
I wouldn't have a problem buying another gain twist barrel again, but I didn't see enough of a benefit to specifically search for another one either. Granted, the sample size has been extremely small so far. Most of the time I've found there is an accuracy node that is easily achievable with either rifling type, so the claimed velocity advantage is a moot point to me. If there was some empirical evidence showing one was better then the other...we would all be using it.
Frank, I really appreciate your thorough answer. I wasn't directing the question at Bartlein, but your answer is really appreciated.
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Like I said it's not for everyone. The "T" would have been ours. That's what we call it.
Later, Frank
Bartlein Barrels
Wilwith1l, Your welcome!
I posted this pic. in the rimfire thread/forum also but will post it here also as we are talking about gain twist.
The rifle is a Marlin Ballard 6 1/2 Rigby off hand rifle. Made around 1885. Original caliber most likely would've been .32-40 or .38-55. It was sent to the Stevens factory real early 1900's. The gun was rebarreled and converted to .22rf. The barrel is marked Stevens-Pope. The rifling has 8 grooves and a left hand twist and is gain twist also. 18-16.5 twist. Remember back then they were shooting lead bullets and the .22rf for the most part are still lead bullets. The gun shoots great. Steve tested it with a bunch of RF ammo he had laying around. Federal Ultra Match (UM1) shot consistently in the mid. .2xx's at 65 yards.
Later, Frank
Bartlein Barrels
