General discussion > Black Powder Shooting

Gain Twist

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JHeath:

--- Quote from: Carl Young on January 07, 2022, 04:46:56 AM ---Bartlein barrels https://www.bartleinbarrels.com/barrel-faq:


 What has been conveyed to us and it goes back to Popes 1st point is that shooters have noticed that they can run a slightly heavier powder charge vs. a shooter with a straight twist barrel. As the bullet is starting easier into the rifling my only guess is the pressure isnít spiking as fast or is delaying the pressure curve. Hence forth they can get more velocity out of the gain twist barrel. I feel pressure is pressure and that the twist doesnít have anything to do with pressure for the most part but my only guess is that the gain twist like I said earlier is delaying the pressure curve...

If you want to go further get a copy of The Story of Pope's Barrels by Ray M Smith

--- End quote ---

Extending the leade on a barrel I have read can allow for more velocity, the gas has volume in which to expand and the bullet has distance to overcome standing inertia before engraving pressure and the standing inertia of non-rotating mass are added. It takes energy to rotate an object so I guess fast twist at ignition is like kicking a bowling ball and gain twist is like giving a bowling ball a gentle push and then kicking it.

Dphariss:

--- Quote from: JHeath on January 07, 2022, 05:25:30 AM ---
--- Quote from: Carl Young on January 07, 2022, 04:46:56 AM ---Bartlein barrels https://www.bartleinbarrels.com/barrel-faq:


 What has been conveyed to us and it goes back to Popes 1st point is that shooters have noticed that they can run a slightly heavier powder charge vs. a shooter with a straight twist barrel. As the bullet is starting easier into the rifling my only guess is the pressure isnít spiking as fast or is delaying the pressure curve. Hence forth they can get more velocity out of the gain twist barrel. I feel pressure is pressure and that the twist doesnít have anything to do with pressure for the most part but my only guess is that the gain twist like I said earlier is delaying the pressure curve...

If you want to go further get a copy of The Story of Pope's Barrels by Ray M Smith

--- End quote ---

Extending the leade on a barrel I have read can allow for more velocity, the gas has volume in which to expand and the bullet has distance to overcome standing inertia before engraving pressure and the standing inertia of non-rotating mass are added. It takes energy to rotate an object so I guess fast twist at ignition is like kicking a bowling ball and gain twist is like giving a bowling ball a gentle push and then kicking it.

--- End quote ---

In some cases the velocity can be increased by the increased powder charge or pressures can be lowered with the same charge. But I canít get into examples without getting too far into brass suppository  guns.  And It has nothing to do with MLs. AND with BP it may result is larger velocity variations and other accuracy issues. But in a breech/muzzleloader this would be different I suspect.
The gain twist with a CLOTH PATCHED bullet, like the Picket, can eliminate stripping the patch since the projectile is not spun up as fast and once its rotating the twist can be increased to what will give the best accuracy. But unless using a large RB close to an ounce or more and trying to spin it too fast I canít see it being important to the RB.
Nor do I think that there is anyway to start a bullet with a gentle push with BP. The initial acelleration is pretty energetic with this propellant. More so than with grey powder.

Tim May:
Thanks for all replies. Just undisighted
What to with this barrel it is marked
J.J.J.J.
Large. No other stampings
Tapered 1and 1/8 to 1 in. 45 cal.
36 in long gain twist.
Thanks
Tim

recurve:
.54 at 50 yds group sight in then adjusted front sight
Talk to Bobby Hoyt, he  does gain twist as does Colerain
Gain twist.      Bobby Hoty you have to call

This is from the colerain web site
We offer GAIN/progressive twist rifling as an option in our barrels. All gain twist barrels will shoot round balls very well, plus allow the use of conical and saboted bullets. To arrive at the desired curve for rifling gain twist some precise mathematical figuring is required, in other words you cannot just throw in some curve and hope it works. With gain twist the bullet starts at a much slower twist rate than what it leaves the muzzle at. As the bullet travels down the bore the twist rate starts to increase, first slowly then faster as it goes. For instance, letís say in a 42Ē barrel the rifling machine is set to cut a twist of around 1 in 96Ē at the breech then the muzzle twist rate will be around 1 in 48Ē. If the twist rate is increased to a faster rate at the muzzle the twist rate at the breech will also increase, but at a lesser rate than the muzzle. This type of rifling in a muzzleloader barrel comes literally as close as possible to give one barrel the ability to handle most forms of bullets and with a high precision of accuracy. If any of you shoot long range centerfire rifles you might have noticed that the big names in high power barrel manufacturing have also started to make GAIN twist barrels.

Our gain twist barrels are being used by hunters and target shooters. Hunters in the western states are hunting large game because of the ability to shoot conicalís and saboted bullets. We offer gain twist in all rifled calibers except 36 cal.

Standing Bear:
I agree w DPfarris. All projectiles resist sudden acceleration forward (recoil) and rotation (torque). The heavier the projectile the more resistance. All PRB have only a small tangent engaging the rifling even w a tight combination and deeper rifling like .012Ē. A larger caliber PRB, say .50 up, when fired with heavy charges can cause the condition called stripping the rifling.  A gain twist starting the rotation at a slower pace and increasing through the barrel will have less tendency to strip the rifling and predict greater accuracy.

The reverse is true IE 1/48 straight twist, .004-005Ē rifling, .490 ball, .005Ē patch probably wonít be very accurate with 120 gr FFFg.

Just my $2. Pennies arenít worth much anymore 

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