Gain twistrate barrels and chamber pressure

[Nathan1990]

So i recently learned about gain twist barrels and wondering has anyone out there done extensive testing on them in correlation to chamber pressure and velocity cause i know a more aggressive twist barrel increases friction/forces on the bullet therefore increasing chamber pressure and conversely lower twistrates have less friction/forces reducing chamber pressure
So lets say in a prefect world where you had the ability to make a barrel in whatever twistrate you wanted and you had a physics engine that could simulate the chamber pressure when the bullet is at any point in the barrel during the firing process
So someone could theoretically tune a gain twist barrel to make to to where you could fire heavier bullet with an above max load of powder but start with a very slow twist rate like a 1-12 to keep the chamber pressures to an acceptable level but increase the twist rate quickly to let say 1-6 for the sake of discussion to increase chamber pressure as it goes down the barrel to try and keep the chamber pressure curve more flat (as the gasses expand) and keep the force pushing the bullet down the barrel more consistent and have more total force acting on it through out the length of the barrel without increasing chamber pressure above acceptable levels therefore allowing you to use more powder cause the slow twist rate at the beginning keeping pressures down to an acceptable level and then try and keep the chamber pressures higher further down the barrel using a gaining twist rate and thus increasing velocity without increasing chamber pressure i think this would also help with more complete powder burn as well cause your trying to control that pressure wave of expanding gasses using the forces on the bullet from your gaining twistrate versus on a normal barrel where ur chamber pressure is at it’s highest right when the primer is ignited basically goes down progressively as the bullet moves down the barrel and the gasses expand

Idk i’m no physics expert but learning about gain twistrate barrels had me thinking on the theoretical possibilities and what you could do with custom gain twistrate barrels

 

[83cj-7]

This:

Radical Gain-Twist Barrel for AR and High Power Rifles « Daily Bulletin

Gain-twist refers to a form of barrel rifling where the twist rate gets tighter over the length of the barrel. For example, a gain twist barrel might start with 1:12 twist and finish with 1:8 twist.

bulletin.accurateshooter.com

Although interesting, I’d think if it was some sort of magic, barrel companies would have been pushing this for a long time.
You should read about “bore rider” throats. Also another interesting topic about pressure and speed. Heard lots about it years ago but not so much now.

 

[david2duck]

There is some good info on snipers hide about gain twist, and how a left twist may be better for some shooters over a right twist. Interesting stuff.

 

[DangerRanger]

I would call Bartlein/ find Frank Green on a forum and ask.

Your question seems specifically about research of chamber pressure changes as a result of gain twisting. I doubt there is much out there on that specific topic, if there is Bartlein is a good shot at it. I say this because Bart is one of the industry leaders in Gain twisted barrels, and also one of the major sources of pressure testing/testing for manufacturers. That's a combination of expertise that is quite close to optimal for people looking at exactly what you are asking.

I also dont think the will "sell" you on the tech. Hell, they once talked me out of one.

This is terribly anecdotal so I probably shouldnt get into it, but my current rock is gain twisted slightly because all of them are and I havent noticed any subjective early pressure signs.(possibly the opposite) Unfortunately for common folks like us, we never truly know chamber pressure, we are always banking off subjective signs that are masked from many other variables like bore diameter, brass quality, ignition differences, action differences etc. It takes a lot or resources to reduce those variables on a scale large enough to make conclusions on such a specific hypothesis, someone like Bart or maybe Applied Ballistics may have them

 

[wind gypsy]

Going off memory here but doesn't litz test the twist rate/pressure theory in one of his books? IIRC the results didn't indicate a statistically significant increase in pressure.

Edit: maybe it was only velocity i was thinking - here's a related link: http://bulletin.accurateshooter.com/2015/02/does-barrel-twist-rate-affect-muzzle-velocity-litz-test/

 

[Flyjunky]

Go to accurateshooter and do a search because it's been discussed there with Frank chiming in on the subject.

The other option to get a similar affect is +P by defensive edge.

 

[QuackAttack]

Bore dimensions will affect pressure far more than gain twist.

As long as you aren’t doing a tight bore, pressure isn’t really going to change much.