3f or RS in a brass framed revolver.

[Don]

Been doing some chronographing of RS and 3f loads in my brass framed revolvers. Typically I load 25 grains of Pyrodex P or 3f black in my .44's as I consider that the reasonable max for such guns. I have found that 30 grains of RS or 3f have similar performance to the smaller loads of 3f/P. Logic tells me that with similar performance that pressures and stresses should be similar. Am I missing something or does this make sense to others?

Don

 

[Loyalist Dave]

Um not quite sure what you're asking...if you are using the same bullet, and are increasing the powder by 5 grains (20%) but getting identical or slightly higher velocity on the chrono? Correct?

The question is then, what do you mean by "similar performance"? Is it an increase of only 20 fps or less, or is it say 50 fps or higher and consistent? I'm wondering if it's simply because the ball is closer, granted not by much, but closer to the end of the chamber, so the pressure does go higher, but you have less time for the ball to accelerate before it exits the chamber. So you're trading off a bit on pressure vs. acceleration time and ball exit?

If you're using .451 ball, there is very little of the ball actually sealing the chamber. If you went to .454 ball, you might see a rise in velocity as you'd have a split second more of a gas seal, and you have to also overcome the added friction of more ball surface against the chamber walls = more buildup of pressure with a .454 vs. a .451.

The other theory would be simply that the last few grains of powder that ignite are doing so as the ball is moving..., which means the chamber itself is increasing in volume as the pressure goes up, so does the chamber volume as the ball moves forward, and perhaps the last of the powder burns just as the seal between the chamber wall and the surface of the ball is lost = little if any gain. So you're just wasting powder, and yes you're getting close to the same pressure.

I wouldn't assume though, that the latter theory is the best. I'd simply use less powder if you're getting nearly the same result, and keep the pressures low. In fact I found my brass framed "Confederate Navy" revolvers liked under 20 grains of 3Fg for target purposes...with a couple of wool wads between the powder and the ball.

LD

 

[Billnpatti]

If the only thing you are changing is the powder then MV equates to breach pressure. Same MV, same breach pressure. If you change anything else that all goes out the window. With modern revolvers using smokeless powder, it is an entirely different thing. Then you have to take into account the burning rate of the powder. With black powder and its substitutes, when you are talking about the same granlulation, there is not all that much difference in the burning rates when compared to the differences in smokeless powders. There is a rule of thumb to reduce your powder charge by about 10% when going from real black powder to a substitute to get the same MV. Of course, you do know to NEVER use smokeless powders in your revolver.

I will caution that a brass frame revolver is not intended for heavy loads, it is more of a target or plinking pistol. Heavy loads will eventually cause the frame to stretch. I know there are folks who will tell you that they have shot heavy loads in their brass frame revolver for years with no problems. I won't question their word but I will say that I wouldn't do it. Just enjoy plinking or target shooting with your brass frame revolver using light to medium loads with round balls. If you want to go magnum, get a steel frame revolver such as a Ruger Old Army and blast away. It can take it.

 

[coloradoclyde]

Logic tells me that with similar performance that pressures and stresses should be similar.

Don

I'll disagree with that....I think you are painting with a very wide brush....
In fact!....in the cartridge world trying to achieve similar velocities with different powders whether they are high or low, can cause a catastrophic failures.....
That said:
BP and substitutes are much more forgiving and their velocity range is more limited....BUT! This is no reason to throw caution, safety and common sense, out the window...

 

[necchi]

Am I missing something or

Yep.
You've likely reached the wall with the 25grns of P.
Meaning your revolver has/is using the powder the best it can,, the short chamber, the open area of the chamber/forcing cone and the short barrel simply can't use anymore powder effectively,, it can't move the ball any faster then it's all ready going.
Adding more powder will increase the chamber pressure,, but with the short travel of the ball, it won't increase the speed. All it does is put more pressure on the sidewalls of the chamber and push back harder against the brass frame.

 

[rodwha]

That's simply not true, especially not at such a mediocre powder charge.

In these chronographed results you can clearly see the velocity goes up with every increase in powder charge:
http://poconoshooting.com/blackpowderballistics.html

 

[Don]

Loyalist Dave, I'm actually getting slightly lower velocities with the RS. Everything else is the same. Same size ball with a little lube on top. I guess what I'm asking is do others think I'm abusing the gun with the RS if velocities are the same as with the P.

Don

 

[coloradoclyde]

I'm actually getting slightly lower velocities with the RS. Everything else is the same. Same size ball with a little lube on top. I guess what I'm asking is do others think I'm abusing the gun with the RS if velocities are the same as with the P.

Don

The lower velocity with RS pyrodex is to be expected....
In case you didn't know P grade pyrodex is the 3f equivalent and RS pyrodex is the 2f equivalent....
Additionally the general rule is that as granulation size increases the burn rate decreases....Creating less velocity and pleasure.

Why someone would want to use RS in a revolver boggles my mind though....

"Are you abusing the gun by using RS pryrodex" ?????
Not in my opinion.... It should produce less recoil and pressure because the powder burns at a slower rate.