Gain Twist

[LilysDad]

I didn't want to detract from Gaeckle's post. He made the following statement concerning his rifle's barrel;

"It is a 50 caliber with a twist of 1 in 66 that slightly speeds up to 1 in 60."

How does that barrel work? How does it compare to a barrel that is 1 in 60 from start to finish? I would think that the RPM at the point where it leaves the barrel is the only thing that matters.

[Longknife]

Gain twist has been experimented with since the mid 1800's. Some highly regarded rifle makers used it with great success and claimed it was more accurate than a regular twist. I have a gain twist barrel in.40 cal. 1-60 to 1-40. Its an original rifle re bored and rifled by Bobby Hoyt. It is extremely accurate. I won many matches and harvested many squirrels with it in the '80's. I have found that if you have confidence in a barrel and believe it is super accurate then it usually is....   The debate goes on..........Ed

[Dphariss]

I didn't want to detract from Gaeckle's post. He made the following statement concerning his rifle's barrel;

"It is a 50 caliber with a twist of 1 in 66 that slightly speeds up to 1 in 60."

How does that barrel work? How does it compare to a barrel that is 1 in 60 from start to finish? I would think that the RPM at the point where it leaves the barrel is the only thing that matters.

The gain twist appeared in the 1830s+- SFAIK with the cloth patched picket bullet. They used a pretty high gain. 48 or slower to 30"+-. Thinking the slow initial twist helped reduce stripped patches. Remembering that in my experience and that of others that the picket requires significantly more powder than the RB in the same rifle. My 40 cal shot best at 80 gr of FF Swiss. I lost interest and did not go higher. This was a straight 48" twist. While I am sure that at 200 it would out shoot the RB at 100 it would not.
The gain never really fell from use. Harry Pope used it. And its still possible to get gain twist barrels for MLs or for moderns. However, it has been found that gains much over 1" may put a lot of stress on a bullet with a long bearing surface (picket bullets have bearing surface about like a RB). But even a 1/2" gain may be beneficial.  A friend and serious shooter was associated with company doing such barrels and tells me they REALLY shot well. How could a slight gain or even an extreme 60" to 30" be better?
It is essential that the twist be uniform. HOWEVER. back in the day, given the state of the art so to speak, it might be possible to have a rifling guide that produced a slight reverse gain. IE slower at the muzzle. With a RB this probably will not mean much. But with a bullet it can lead to serious issues. So this was another advantage to the gain twist. Modern button rifled barrels when the button is simply pushed through the barrel are known to sometimes have variations in twist along the length of the bore. Or so I have read and there are people where are or were, using modern equipment to check barrels for this. So if you had a blank that had a slowing of the twist at the muzzle it was possible to shorten it at a point where the twist was uniform. Or so it was said.
I have two gain twist heavy rifle barrels by McLemore. The 50 I shoot now and then but since it is strictly a rest rifle and we are not doing rest matches right now it don't get much use. But it would win any chunk match in the country from the winning strings I have seen posted. With a shooter with really good eyes there is no reason it would not produce a 2" 10 shot string at 60 yards.

Dan

[WadePatton]

...
How does that barrel work? How does it compare to a barrel that is 1 in 60 from start to finish? I would think that the RPM at the point where it leaves the barrel is the only thing that matters.

What I have pulled from the debate over the years is that so long as the rifling rate is constant, or increasing by -any- small amount near/at the muzzle, then the gun will shoot.  But if the rifling rate has any decrease in rate near the muzzle then it could likely be a problem.  While we like to think of "fixed" rates or measurements as such, they rarely are when you consider the realities of tolerances and production work.  There are always tolerances, within those limits all measurements are considered equal.  And that's where you get tight/loose fits sometimes with "same" sized items.  It's the combination of one thing that ran big/small inside the tolerances and the other thing ran to the opposite end of tolerance for its production.

Rates of twist are firmly connected to velocity needed for stabilization.  It takes very little twist to stabilize a ball, and the faster you push it, the lower you can go with ROT for good stabilization.  Higher ROT are only necessary for two things: increased mass of projectile, lower velocity desired or possible (pistol, e.g.).

I have yet to ever see an argument that a decreasing rate is good, and am satisfied that a fixed rate (which can have some deviation in it) or increasing rate will shoot with a proper load work up and good components/consistency.  Buying a bbl made with gain twist ensures that the rate will -not- be decreasing at the muzzle. 

Some say that match grade bbls are made longer than desired then precisely measured to find some minute amount of measurable gain (although rifled with a standard rate) and then cut at that point and breeched on the other end.  Cut a gain twist and such isn't necessary, but you don't see a lot of makers offering GT. 

Any time someone says I cannot get this one to shoot--after they've tried for months and hundreds of shots and good bench form, I suspect a slight, but imperceptible without precision measurement, decrease in twist may be the culprit.

Thankfully modern production tolerances are good enough we don't see a lot of that. It'd probably make me nuts hand-cutting the rifle of a tube and knowing all this... so I buy pre-mades.


Oh look, here's Dan.  Dan has one of the most mentioned guns on the forum when it comes to gain-twist.  And you just heard from him on the matter.  Thanks Dan.

[yulzari]

As long as the ball does not strip the rifling all it knows is the spin as it comes out.

[S. Garbe]

Gentlemen,
I agree with both Wade and Dan. One wants a uniform or slightly gaining twist with no "dead" spots. When we produced barrels at Ballard, we did them with 1/2" gain from breech to muzzle. This worked to virtually eliminate negative variations in twist, i.e. "dead spots" and make for a very consistent, slightly gaining twist. No real magic about a gain twist other than I believe it also provides for a slightly choked barrel. Slugging a barrel before you cut it off to length and checking for tight and loose places can also save you a lot of time, powder and lead.

Like anything, you get what you pay for with barrels. Quality costs money.

Steve

[Gaeckle]

I didn't want to detract from Gaeckle's post. He made the following statement concerning his rifle's barrel;

"It is a 50 caliber with a twist of 1 in 66 that slightly speeds up to 1 in 60."

How does that barrel work? How does it compare to a barrel that is 1 in 60 from start to finish? I would think that the RPM at the point where it leaves the barrel is the only thing that matters.

The rifling machine came with that lead in that twist rate. Everything was hand built and the lead is basically a one inch steel bar that was twisted with a pipe wrench while held fast to a support. Over the year's this machine was improved by others , but the lead bar was left alone.
I think that straight twist barrels will shoot just fine, and that basic fundamentals of powder, patch, ball and shooter's skill all determine accurate shooting. Plus, lots of practice.
I have another rifle, 50 caliber, that has a barrel from the same machine. For me it shoots great. My son was using it over the weekend. We found out that for him it shoots about  6 inches to the right. For me, I can hit a pop can at 25 yards.
I think a lot has to do with the shooter, vision, hold and follow thru, stance, and a whole host of other variables.
Consistency, I think is also a key ingredient.

[Craig Wilcox]

My mind comes up with a big question that may have been partially answered above"

How is a gain twist made?  Is the rifling guide slightly steeper toward the muzzle end?  Mathematically, I can see how a slightly steeper rifling guide would cause the increase from, say, 66 to 60, or some other number.  And is this done just a few inches from the muzzle, or halfway along the barrel?

Them old folks sure came up with some great ideas!  Even the flintlock was a huge step forward.

[Hungry Horse]

 I’ve never seen an antique muzzleloading round ball gun with a gain twist. Gain twist was all the rage when shooters stopped using patched round balls, but I have never seen a vintage gain twist gun that I could absolutely identify as a round ball gun.

  Hungry Horse

[Ric Carter]

Harry Pope said he couldn't see a dime's worth of difference.

[Bob Roller]

Pope made gain twist barrels but he wasn't using a round ball.
N.G Whitmore,maker of high grade target rifles used gain twist and 12 grooves
and his guns were considered unfair competition accord to Major Ned Roberts.
In our time Bill Large made them for round balls and they were very accurate
and Jim McLemore made them as well and I have heard only good reports on them.
Whitmore used a picket bullet,sometimes referred to as a ball and when he tested
the rifle he made for General Grant he tested it at 110 yards and fired 10 ahots
that all were under and inch using only the metallic sights the gun is displayed with.
  I tried to get Bill Large to copy the Whitmore 12 groove barrels but that was late
in his career and he wasn't interested.Walter Cline,a founder of the NMLRA had a
superb 43 caliber Whitmore and it was a real match winner.It was the same pattern
as the Grant rifle and there have been several more turn up over the years.
The Whitmore barrel Bill Large had was this pattern which was one third octagon and
two thirds round and at one time it had a false muzzle.
Bob Roller

[Dphariss]

Harry Pope said he couldn't see a dime's worth of difference.

Which then begs the question. "Why did he use the gain then?". AND he was not making barrels in the 1830s-40s with much cruder equipment.
Consider the things that Brockway told Roberts. I firmly believe he was feeding him BS on some things. Like shooting increasingly large charges until finding   unburned powder and considering that a slight reduction of a few grains was then the right load. In my experience it would take an awful lot of powder behind a slug to produce this even with FG powder.  Then Roberts comments on picket bullets which seem a little "off" to people shooting them today.

 I think the "take the barrel out of the lathe to straighten it while boring then put it back in and continue was questionable. Could be true. But it would be a huge PITA IMO to do this once everything was centered. Then having to put a bent bar of steel back in the lathe and not have a wobble?  But I don't know what equipment he used either.
 
Given the competitive nature of such things back in the day, I can't see Pope passing on info. Like when someone asked him how he lapped a gain twist barrel. His answer was not informative. I suspect that these barrel makers were not much for spreading what they knew around. They sold rifles because their rifles won matches so there is no reason to help out someone else.
There really is no magic in making a good rifle barrel. A good uniform bar of steel and CARE and knowledge in drilling, reaming and rifling it.  Even some barrels  with uniformity of bore "issues" that  Pope would pitch likely in the scrap pile can shoot surprisingly well. Note as good as a really good barrel but so good most people would never know. Yes, I like SPG used to work in a place that made rifle barrels and did some experimenting though I was not the barrel guy. But the barrel guy did it for me.

Dan

[Scota4570]

I wonder?  IF you have a gain twist the change in pitch would have a tightening effect on the bullet.  This would act like a choke and lessen any looseness caused by the bullet's travel over the length of the barrel.  We know choke is good, maybe gain twist enhances accuracy for the same reason. 

If it were about lessening the torque acceleration and shearing forces one could use courser powder and achieve the same thing. 

[Hungry Horse]

 The problem with a gain twist shot round ball, is the contact area on the bullet is exceedingly small. This can be compensated for by adding more grooves, but that also reduces the lands. The increased number of grooves creates more opportunities for patch leaks, and  burn throughs. If you really love fiddly stuff, your going to love a gain twist round ball barrel.

  Hungry Horse
 
 

[Marcruger]

I noticed the Steve Garbe has joined us.  Though he only has one posting, do not make the mistake of thinking he is a novice or beginner.  He has massive experience with black powder, patching, and launching lead.  It is worth reading and digesting his words. 
God Bless,   Marc

[Dphariss]

I wonder?  IF you have a gain twist the change in pitch would have a tightening effect on the bullet.  This would act like a choke and lessen any looseness caused by the bullet's travel over the length of the barrel.  We know choke is good, maybe gain twist enhances accuracy for the same reason. 

If it were about lessening the torque acceleration and shearing forces one could use courser powder and achieve the same thing.

In bullet guns, cylindrical type bullets, not the "Picket", to much gain will produce rifling marks that are distorted. Look like "skid" marks.


Dan