Progressive twist rifling

Mohawk3a

Mohawk3a

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Oct 8, 2010
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#1
Can someone tell me how to determine the proper twist required to stabilize a bullet when using a progressive twist. Is the end twist rate (at the muzzle) the number you use? Does the lighter twist rate at the breach take away from the heavier twist at the muzzle? If so, how much? Thanks
 
#3
Re: Progressive twist rifling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mohawk3A</div><div class="ubbcode-body">Can someone tell me how to determine the proper twist required to stabilize a bullet when using a progressive twist. Is the end twist rate (at the muzzle) the number you use?
</div></div>

Use for what? If you are talking for bullet stabilization, then, yes, the twist rate at the muzzle is the one that counts.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mohawk3A</div><div class="ubbcode-body">
Does the lighter twist rate at the breach take away from the heavier twist at the muzzle? If so, how much? Thanks</div></div>

Take away from in what way? My thought is that by gradually accelerating the spin, progressive twist is probably easier on the jacket than a high twist fixed spin bore... which doesn't matter for Sierra, but might matter for a lot of the custom bullets out there.

Also, you might be looking at less friction at the breech part of the barrel... tough to figure the impact on that. I would think that it could offer extended barrel life (or not). It could offer reduced pressures... which would be accompanied by reduced velocities (or not). I think progressive twist is going to be a lot like moly or boron nitride with some folks swearing by it and some folks swearing at it...

Still, it seems like the latest deal.
 
#5
Re: Progressive twist rifling

i think you are refereing to is a gain twist and the twist at the muzzle is what counts. the downside is that the lands in the barrel are leaving a different immprent in the bullet at the chamber end than at the muzzle end ad some people claim that to cause a loss in accuaracy and others swear by the gain twist. the millitary has been using gain twist barrels on alot of things for years i have an old 20mm vulcan barrel that i picked up somewhere that has a crazy looking gain twist in it and it actually runs the oppisite way it is a faster twist at the breech and slower at the muzzle
 
#6
Re: Progressive twist rifling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TerrorInTheShadows</div><div class="ubbcode-body">WTH? This is actually a real thing?

</div></div>

Yeah its real.
 
#7
Re: Progressive twist rifling

search here, George from built a rifle with a gain twist and from what they say it's a beutiful performer. Also if you want info cantact the Bartlein guys. They are the ones leading the way with this and built George's barrel
 
#9
Re: Progressive twist rifling

Rock Creek also can provide 'gain twist' blanks. I have a 6 and 6.5 laying around here somewhere. 6.5 is from 8.8" to 8.5", think 6 is either the same .3 change or .5, cannot remember. I am a blank whore so I lose track sometimes on what I have and what contours, twists etc
smile.gif
 
#10
Re: Progressive twist rifling

Gain twist rifling was first used somewhere in 19th century, IIRC.

I have a custom handgun that I had built a few years ago with gain twist rifling. It shoots like a laser.
 
#11
Re: Progressive twist rifling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coues103</div><div class="ubbcode-body">...the downside is that the lands in the barrel are leaving a different immprent in the bullet at the chamber end than at the muzzle end ad some people claim that to cause a loss in accuaracy...</div></div>Please explain.
 
#12
Re: Progressive twist rifling

Several manufacturers are putting out gain twist barrels, Rock is one, Bartlein is another (they call theirs transitional twist). Many only gain a slight amount, say start at 11 and exit at 10. If you read George's Crusader thread, I think he is using one like that with a slight gain.

Benchresters have been using them for a considerable period and doing well with them. Do a search at Benchrest.com on Gain twist barrels ....

While I do not profess to be any expert in gain twist barrels, I believe that the exit twist is the final word on the RPMs that the bullet will be spun to, so if it exits at a 10" twist, it imparts the same twist on the bullet as a standard 10" twist would.

I believe that artillery has been using gain twist since WWI or maybe its WWII .. but its been a long time. I just did a quick and dirty search and these two popped out at me.

http://riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htm

http://www.midwayusa.com/guntecdictionary.exe/showterm?TermID=2535

JeffVN
 
#13
Re: Progressive twist rifling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coues103</div><div class="ubbcode-body">i think you are refereing to is a gain twist and the twist at the muzzle is what counts. the downside is that the lands in the barrel are leaving a different immprent in the bullet at the chamber end than at the muzzle end ad some people claim that to cause a loss in accuaracy and others swear by the gain twist. the millitary has been using gain twist barrels on alot of things for years i have an old 20mm vulcan barrel that i picked up somewhere that has a crazy looking gain twist in it and it actually runs the oppisite way it is a faster twist at the breech and slower at the muzzle </div></div>

This makes perfect sense to me, as the bullet is being accelerated as it travels down the bore; since it starts off slow, a faster twist rate makes more sense at the chamber. It also seems to me that the lands will impart a different imprint on the bullet at different stages down the barrel; this is required, in fact, by geometry. I'm not sure why anyone would want to do that.
 
#14
Re: Progressive twist rifling

I got the name "progressive twist" off bartlein's web site. That is what term there are going with for the "gain twist" barrels, from what I understand. Thanks for the help. I figured the end twist is what mattered. I wanted to make sure the lack of twist at the breach didn't take away from the twist number at the muzzle.
 
#16
Re: Progressive twist rifling

If anybody knows where research, testing or experience on this subject has been posted, please point me in the right direction. Thanks
 
#17
Re: Progressive twist rifling

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coues103</div><div class="ubbcode-body">...the downside is that the lands in the barrel are leaving a different immprent in the bullet at the chamber end than at the muzzle end ad some people claim that to cause a loss in accuaracy...</div></div>Please explain. </div></div>

Seems pretty obvious to me that changing the pitch of the screw part way down the hole isn't going to be good for the screw.

Part of the idea with lead bullets is that soft lead is less likely to strip if the pitch doesn't start out fast.

In modern guns, I figure it's marketing, though I'll listen to more experienced shooters on this, and there are many.
 
#20
Re: Progressive twist rifling

No, it's gradual and continuous.
You engrave a slow twist, then it gets steeper, then steeper, all the while moving jacket metal as the angle of the lands changes, embedded in the jacket.

Put a lead slug in the breech of a gain twist barrel, put a rod in from the muzzle and one from the breech and beat on the bullet to fill the grooves.

Now push it out the muzzle.
You will NOT have pretty CSI grooves.
 
#21
Re: Progressive twist rifling

Excuse my ignorance but what is the gain from this other than distorting bullet jackets and lead. It was stated earlier that this was the reason was to help prevent stripping lead bullets. If you shove an inclined plane into a reversed non matching inclined plane your will definitely have distortion yes?
 
#22
Re: Progressive twist rifling

A little FYI... Gain twist rifling has been around a long time. All of the "Original" Colt Cap and Ball revolvers from the Civil War Era have Gain Twist Rifling. That's one of the ways to tell the real thing from a good fake.
 
#23
Re: Progressive twist rifling

There is a big difference between the Gain of Old and what Bartlein is doing. They are the <span style="font-weight: bold">"Only" </span>company <span style="font-weight: bold">"Ever"</span> than can produce a consistant gain from one end to the other. Other companies have and still sell Gain Twist barrels but none of them can produce a perfect gain from Breech to Muzzle.

If you dont believe me call them all and ask for the gain to be guarenteed consistant from ened to end and if they can also guarentee thats its 1-9.545 to 1-8.275 then call Bartlein
 
#24
Re: Progressive twist rifling

In the interest of clarity: Some manufacturers quicken the twist slightly in the final few inches on all their barrels, even when the barrel is manufactured on an old P&W gear-driven press. That's not really a 'gain-twist' barrel, though.
 
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