Gain Twist Barrels - Much ado about nothing?
- Thread starter adamsgt
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O
Old Gunner
Guest
The idea pops up every so often, and never really catches on. The last mass production rifles with gain twist that I can think of off hand were the Italian 6.5 Carcano rifles.
In black Powder days gain twist may have served a purpose, but I can't see any real advantages when modern high velocity bullets are used.
Metal jacketed bullets with long bearing surfaces don't react quite so well to a gain twist as the old short bearing lead slugs or round ball did.
In black Powder days gain twist may have served a purpose, but I can't see any real advantages when modern high velocity bullets are used.
Metal jacketed bullets with long bearing surfaces don't react quite so well to a gain twist as the old short bearing lead slugs or round ball did.
jackie schmidt
New member
Not Quite
The majority of the records that were shot at the Nationals were shot with gain twist barrels.
Gene Bukys won the Benchrest World Championship with a Gain Twist.
Of course, there are a lot of mediocre aggs being shot with them as well. But I suppose if you get a good one, they do shoot quite well........jackie
The majority of the records that were shot at the Nationals were shot with gain twist barrels.
Gene Bukys won the Benchrest World Championship with a Gain Twist.
Of course, there are a lot of mediocre aggs being shot with them as well. But I suppose if you get a good one, they do shoot quite well........jackie
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Gerry
Guest
Gain twist barrels
I had one put on last year and have been testing. The rifle is shooting very tight especiaally at 200yds.
The exit twist is 13 1/4 . I think LOu has been using one along with TONY Boyer. I haven't quite figured out what is really happening. I'm playing with twist ratios and one bullet shape and weight. It may just be the 13 1/4 exit that has improved the group sizes at 200. I'm still playing and will test more next year, I know everyone like s the 14 or 13 1/2 but i still think something else may work Better. It may be that the gain is the thing that is working really well for me.
I had one put on last year and have been testing. The rifle is shooting very tight especiaally at 200yds.
The exit twist is 13 1/4 . I think LOu has been using one along with TONY Boyer. I haven't quite figured out what is really happening. I'm playing with twist ratios and one bullet shape and weight. It may just be the 13 1/4 exit that has improved the group sizes at 200. I'm still playing and will test more next year, I know everyone like s the 14 or 13 1/2 but i still think something else may work Better. It may be that the gain is the thing that is working really well for me.
O
Old Gunner
Guest
Probably been a good deal of work put into getting the barrel making process down pat, but I suspect that at best such a rifling pattern would be limited in the weights and construction features of bullets it handled well.
PS
The gain twist used in recent years is far less radical, on the order of 1:15 to 1:14.25 in some barrels.
The less radical gain in twist would seem to give much better results than earlier attempts.
Could be perceived improvement is misattributed.
http://www.riflebarrels.com/articles/barrel_making/details_of_accuracy.htm
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Boyd Allen
Active member
With Bartlein using real time computerized control of twist rate, much more exact results and subtle gains can be reliably achieved. Some of the barrels may have as little as a 1/4" change in twist rate. Also, the measurement of twist rate, to verify consistency from breach to muzzle pretty much belongs to the world of buttoned barrels. Single point cut barrels, whether done with Pratt Whitney sine bar machines or the newest CNC equipment are in a whole other class in this respect. A well known California competitor and gunsmith, of many years experience, told me years ago, after switching to Krieger barrels, that he no longer needed his twist measuring machine, because all that the needle did was stay in one place and vibrate slightly. This is not to throw rocks at buttoned barrels, but merely to point out that there are different types of problems involved with different manufacturing methods.
Gain-twist barrels...
are certainly nothing new, but they have never demonstrated indisputable superiority over fixed-pitch barrels for any shooting discipline.
Harry Pope made gain-twist barrels for his breech/muzzle loading lead-bullet rifles, but stuck with fixed-pitch for jacketed, high-velocity bullets. I personally believe that the superior performance of Pope's barrels was due more to his painstaking, careful workmanship than the style of rifling he preferred, and that his barrels would have been as good if all of them had been conventionally rifled. Then, too, I cannot agree with his contention that his form of rifling and loading from the muzzle deformed the bullet less: in fact, it forced the bullet from the fastest pitch at the muzzle to the slowest pitch at the breech, and then back, subjecting the engraved surface of the bullet to shearing forces in both directions, as the pitch changed. The plastic nature of the fairly soft alloys he used may have ameliorated the effects to an extent, but even he recognized that this did not apply to jacketed projectiles.
What is not often discussed are several facts about gain-twist barrels and their effects on the bullet itself: the grooves change width as well as pitch. In a cut-rifled barrel, the grooves decrease in width as the pitch increases, because the aspect of the face of the cutter changes as the angle of attack increases: this would seem to be preferable in a mechanical sense because the changes in the engraved and un-engraved surfaces of the bullet (grooves become wider, while the 'lands' on the bullet body increase in width) help to preclude escape of gas past the bullet. In a button-rifled barrel, the grooves must necessarily increase in width as the pitch is increased, because, unlike the single-point rifling cutter, which has an essentially perfectly sharp crest and clearance behind the edge, the button has lands of finite length in order to push-up a standing wave of barrel material, then ride over it and smooth it in passing, and the only way the pitch can be increased is by driving the button at a pitch faster than the basic one engraved in the button's body - the result is that the barrel grooves increase in width and the lands become narrower, which seems less desireable than the case with cut-rifling. Then, too, consideration of the forces on the button in rifling with a fixed-pitch make one wonder how good the results can be from trying to drive the button at an ever-increasing pitch as it is forced through the barrel: button-rifled barrels already suffer from pitch variations due to such factors as varying hardness of the barrel steel and the lubrication of the bore, and attempting to force it to rotate faster than its basic pitch, on the end of a long rod of less-than-bore diameter (which can be deflected measureably with no more force than the hands can apply), is a very uncertain process.
Finally, gain-twist barrels cannot be lapped in the usual way, for reasons already given. A bore-riding lap can polish the surfaces of the lands, and probably remove any burrs left on the edges of them, but there is no practicable process to polish the grooves, which, by increasing pitch and change of width, prevent a standard lap from being pushed and pulled through the bore.
FWIW.
mhb - Mike
are certainly nothing new, but they have never demonstrated indisputable superiority over fixed-pitch barrels for any shooting discipline.
Harry Pope made gain-twist barrels for his breech/muzzle loading lead-bullet rifles, but stuck with fixed-pitch for jacketed, high-velocity bullets. I personally believe that the superior performance of Pope's barrels was due more to his painstaking, careful workmanship than the style of rifling he preferred, and that his barrels would have been as good if all of them had been conventionally rifled. Then, too, I cannot agree with his contention that his form of rifling and loading from the muzzle deformed the bullet less: in fact, it forced the bullet from the fastest pitch at the muzzle to the slowest pitch at the breech, and then back, subjecting the engraved surface of the bullet to shearing forces in both directions, as the pitch changed. The plastic nature of the fairly soft alloys he used may have ameliorated the effects to an extent, but even he recognized that this did not apply to jacketed projectiles.
What is not often discussed are several facts about gain-twist barrels and their effects on the bullet itself: the grooves change width as well as pitch. In a cut-rifled barrel, the grooves decrease in width as the pitch increases, because the aspect of the face of the cutter changes as the angle of attack increases: this would seem to be preferable in a mechanical sense because the changes in the engraved and un-engraved surfaces of the bullet (grooves become wider, while the 'lands' on the bullet body increase in width) help to preclude escape of gas past the bullet. In a button-rifled barrel, the grooves must necessarily increase in width as the pitch is increased, because, unlike the single-point rifling cutter, which has an essentially perfectly sharp crest and clearance behind the edge, the button has lands of finite length in order to push-up a standing wave of barrel material, then ride over it and smooth it in passing, and the only way the pitch can be increased is by driving the button at a pitch faster than the basic one engraved in the button's body - the result is that the barrel grooves increase in width and the lands become narrower, which seems less desireable than the case with cut-rifling. Then, too, consideration of the forces on the button in rifling with a fixed-pitch make one wonder how good the results can be from trying to drive the button at an ever-increasing pitch as it is forced through the barrel: button-rifled barrels already suffer from pitch variations due to such factors as varying hardness of the barrel steel and the lubrication of the bore, and attempting to force it to rotate faster than its basic pitch, on the end of a long rod of less-than-bore diameter (which can be deflected measureably with no more force than the hands can apply), is a very uncertain process.
Finally, gain-twist barrels cannot be lapped in the usual way, for reasons already given. A bore-riding lap can polish the surfaces of the lands, and probably remove any burrs left on the edges of them, but there is no practicable process to polish the grooves, which, by increasing pitch and change of width, prevent a standard lap from being pushed and pulled through the bore.
FWIW.
mhb - Mike
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Gerry
Guest
Gain twist barrels
The bartlein barrels are double lapped.
First lap is after reaming so the hole is smooth.
second lap is to get rid of any possable burs on the edges of the rifling.
I'm guessing some what at this but i pretty sure that's the why it's double lapped. Maybe frank green can say more on this.
The bartlein barrels are double lapped.
First lap is after reaming so the hole is smooth.
second lap is to get rid of any possable burs on the edges of the rifling.
I'm guessing some what at this but i pretty sure that's the why it's double lapped. Maybe frank green can say more on this.
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C
caroby
Guest
mhb - Mike
Good read Mike... I didn't consider the narrowing cut of cut rifling the groove as pitch increases increasing land width, keeping the seal... Makes sence.
Lap after the reaming process then... After rifling...
As far as lapping, unlike the bullet going in one direction. How does the lead lap stay conformed to the bore as the stroking forward and backward (lapping) is performed..? This again, in a cut gain twist rifled barrel.
cale
Good read Mike... I didn't consider the narrowing cut of cut rifling the groove as pitch increases increasing land width, keeping the seal... Makes sence.
Lap after the reaming process then... After rifling...
As far as lapping, unlike the bullet going in one direction. How does the lead lap stay conformed to the bore as the stroking forward and backward (lapping) is performed..? This again, in a cut gain twist rifled barrel.
cale
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caroby:
The traditional lead lap is fully conformed to the rifling (fixed-twist) by virtue of being cast in-place in the rifled bore, attached to a steel lap rod. The lap is several inches in length, and, after casting is trimmed to remove the casting 'sprue', and charged with lapping compound of the desired grit, then pushed and pulled through the bore until the operator has achieved the desired degree of finish. Multiple laps are often used with increasingly fine abrasives, again, depending on the desired polish and the experience of the operator. The same procedure can be used in the reamed but un-rifled bore before rifling, to mitigate tool marks left by the reaming operations.
A bore-riding lap is usually turned out of some softer metal (brass, aluminum, etc.) to a diameter which will permit a close, but sliding fit in the bore, and the procedure is the same.
It does not matter by what process the barrel is rifled, but the pitch must be uniform for best results from lapping, and a gain-twist barrel cannot be lapped by the first method with a cast-in-bore lap.
mhb - Mike
The traditional lead lap is fully conformed to the rifling (fixed-twist) by virtue of being cast in-place in the rifled bore, attached to a steel lap rod. The lap is several inches in length, and, after casting is trimmed to remove the casting 'sprue', and charged with lapping compound of the desired grit, then pushed and pulled through the bore until the operator has achieved the desired degree of finish. Multiple laps are often used with increasingly fine abrasives, again, depending on the desired polish and the experience of the operator. The same procedure can be used in the reamed but un-rifled bore before rifling, to mitigate tool marks left by the reaming operations.
A bore-riding lap is usually turned out of some softer metal (brass, aluminum, etc.) to a diameter which will permit a close, but sliding fit in the bore, and the procedure is the same.
It does not matter by what process the barrel is rifled, but the pitch must be uniform for best results from lapping, and a gain-twist barrel cannot be lapped by the first method with a cast-in-bore lap.
mhb - Mike
Boyd Allen
Active member
It is comforting to know that the top shooters that have been reporting so favorably on recently manufactured gain twist barrels are simply deluding themselves, and that in reality they have seriously disvantaged themselves due to some sort of mass hysteria, giving the rest of us a better chance of prevailing against them.
C
caroby
Guest
It does not matter by what process the barrel is rifled, but the pitch must be uniform for best results from lapping, and a gain-twist barrel cannot be lapped by the first method with a cast-in-bore lap.
mhb - Mike
Very interesting...! Thanks again Mike.
Still amazes me that barrel makers today can produce such FINE barrels on a consistent year in year out basis.
Least, what I've seen.... My standards may not be tough enough though.
cale
mhb - Mike
Very interesting...! Thanks again Mike.
Still amazes me that barrel makers today can produce such FINE barrels on a consistent year in year out basis.
Least, what I've seen.... My standards may not be tough enough though.
cale
Bob Kingsbury
New member
Harry Pope
He certainly believed in using a false muzzle, but not all of his guns
were done that way. Lead bullets breech seated in front of the case
were common
He certainly believed in using a false muzzle, but not all of his guns
were done that way. Lead bullets breech seated in front of the case
were common
O
Old Gunner
Guest
I doubt anyone is deluding themself, they are certainly doing something right.
Whether they'd get the same results over a wide range of bullets and velocities is a question.
I suspect that its far easier to produce a mediocre gain twist barrel than to produce a great one. If manufacturers were under any real pressure then quality would suffer more quickly when machinery began to show wear and tear after a long run.
Probably why Italy dropped it once wartime pressures kicked in.
Gain twist certainly can produce good results, but whether those results will be consistent or long lasting is a question worth further study.
B
Big Al
Guest
The world record holder for decades used a Pope barrel, had a false muzzle and a lead bullet cast from a Pope mold. He must have been doing something right? And just how many decades was that record held into the modern era?
jackie schmidt
New member
This Is Not The Same Animal
From reading these post, there seems to be a little miss-conception about Gain Twist, especially the gain twist as offered by Bartlien.
First, the gain is so slight that you probably could not even detect it visually. In other words, if you pushed a bullet through a standard 13.5 twist, and one through a Bartlien with a 14.3 to 13.7, the only way you could actually see the diffence in the two bullets would be by measuring the land width with an opticle comparator.
Second, the way Bartlien actually achieves the gain is a product of a CNN controled machine that can vary the twist infinitly. This is some pretty sophisticated equipment. What it allows Bartlien to do is arrive at a gain that 100 percent consistant throughout the length of the bore, rather than a more "abrupt" change that is the product of other methods.
In other words, the way Bartlien achieves their gain twist is different than methods in the past, and is a product of the latest in computer generated motion that regulates CAD-CAM equipment worldwide..........jackie
From reading these post, there seems to be a little miss-conception about Gain Twist, especially the gain twist as offered by Bartlien.
First, the gain is so slight that you probably could not even detect it visually. In other words, if you pushed a bullet through a standard 13.5 twist, and one through a Bartlien with a 14.3 to 13.7, the only way you could actually see the diffence in the two bullets would be by measuring the land width with an opticle comparator.
Second, the way Bartlien actually achieves the gain is a product of a CNN controled machine that can vary the twist infinitly. This is some pretty sophisticated equipment. What it allows Bartlien to do is arrive at a gain that 100 percent consistant throughout the length of the bore, rather than a more "abrupt" change that is the product of other methods.
In other words, the way Bartlien achieves their gain twist is different than methods in the past, and is a product of the latest in computer generated motion that regulates CAD-CAM equipment worldwide..........jackie
O
Old Gunner
Guest
The only time I've fired a rifle that used a false muzzle it was a percussion long range target gun.
The bullets that rifle used were of two piece construction, a softer lead base with a harder alloy nose. The initial impulse of the heavy charge (300 gr of BP) would have deformed the front end of an all soft lead bullet, but harder alloy bullets would not have upset to fill the rifling as well so they used the two piece bullet with a wound paper patch.
Sounds reasonable, the earlier problems with gain twist are a matter of record so it may take awhile before everyone is convinced that consistent results can be expected.
Final comments:
Lest anyone think I was taking a shot at gain-twist barrels, it ain't so! I simply discussed some facts about their manufacture and nature. However... I'll accept that they are better than a good fixed-pitch barrel when such barrels are entirely supplanted in the winners' lists by the former type. My comments were from the viewpoint of a barrel maker who respects workmanship and results: I'll await further developments and give all credit due without quibbling about theory. I'd also be interested in any comments from current makers of gain-twist barrels - if I've gone astray, say where - and quote me accurately rather than inferring what I meant or thought as opposed to what I've actually said.
As for Mr. Pope's barrels: his fame rests primarily on his highest development: the breech-muzzleloading barrels and rifles, used with the false muzzle and Pope accessories and bullets. He guaranteed the best accuracy from his rifles when made on that system.
mhb - Mike
Lest anyone think I was taking a shot at gain-twist barrels, it ain't so! I simply discussed some facts about their manufacture and nature. However... I'll accept that they are better than a good fixed-pitch barrel when such barrels are entirely supplanted in the winners' lists by the former type. My comments were from the viewpoint of a barrel maker who respects workmanship and results: I'll await further developments and give all credit due without quibbling about theory. I'd also be interested in any comments from current makers of gain-twist barrels - if I've gone astray, say where - and quote me accurately rather than inferring what I meant or thought as opposed to what I've actually said.
As for Mr. Pope's barrels: his fame rests primarily on his highest development: the breech-muzzleloading barrels and rifles, used with the false muzzle and Pope accessories and bullets. He guaranteed the best accuracy from his rifles when made on that system.
mhb - Mike