doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com BP pressure curve inside the barrel?

I'm working up some very basic black powder loads using brass Magtech shells, and got to wondering when and where peak pressures occur with black powder. I am guessing that smokeless "keeps pushing" further up the barrel with its various controlled burn rates and has a longer, flatter curve than BP. If the BP pressure curve is a sharp spike just after ignition it would seem that a brass shell might offer a small measure of added strength versus a paper cartridge when shooting black powder in 19th-century breechloaders. Anyone out there know the facts?

The "facts" as I have accepted them, from people who really know what they are talking about, as opposed to the CYA, old-wives'-tales parrots, is that the pressure peak with both smokeless and black powder occurs about 1 to 1-1/2" from the breech face. Very little difference between the two. The fact that the thickest part of the barrels on any gun, very old to very new, is at the chamber area. This pretty much validates the above, doncha think?
The often repeated idea that smokeless pressure peaks out by the forend, "right where yore fangers are", is utter nonsense.
P.S. I have Dupont's Pressure curve graph in my saved documents. I've never learned how to post pictures here but I'd be happy to attach it to an e-mail to anyone who's interested enough to send me an e-mail.
Click on my name, my profile and you'll see my direct e-mail address. Please don't waste your time with a PM.

Jim:

Preach on, brother. Someone needs to spread the TRUTH. Answer this though: besides goverment regs, why would a gunshop need to keep blackpowder in a safe(as per regs), but stack smokeless out on the shelfs? People never question "old-wives'-tales parrots", with the exception of Sherman Bell.

Kind Regards,

Raimey
rse

Jim:
I see absolutely no reason to disbelieve what you have posted.
One can read and hear almost an unlimited number of anecdotal accounts of this matter.
I suppose we, that love the old guns, have often given thought to this and here is what I think.
The chemists and "powers-that-were" had to be aware that their product had,of necessity, to be "better" but not dangerous in the guns that were the shooters of the day. It is folly to think that a man, any man, would simply throw out a useful gun in order to shoot a new powder. I just do not think (logic at play here) that such a powder would have made much an inroad in the market.
When we consider that there were more than a few that held their guns to be sound in design, style and configuration, we can see that any change that generated fear for said gun's being damaged
would have been relegated to the dust bin.
I think that time and much scientific testing has proven that nitro powder shot in a sound old timer is safe. Common sense dictates that the pressure load should not exceed the engineered max for the barrel materials of the time, and one must remember to look to the care of the wood.
If the pressure load is the same, or nearly so, with black powder and nitro powder, coupled with the same mass of the ejected shot, there is no difference as far as the gun goes.
Just some thoughts.
Best,
John

This has been posted several times in the past.



Pete

(The previously mentioned) Sherman Bell "Finding Out for Myself, Part VI, Smokeless vs Black", in Double Gun Journal - Summer 2002 page 19, is modern validation of the mid-1930s Dupont data - not that Dupont's laboratory data needs validation.
Sherman Bell's articles along with Tom Archer's research and prose combine to make the pricey DGJ a must have/must read.
Too bad John Brindle passed away so early as his written works in the early 1990s DGJ were pure gold also.

The reason for at least some of the different regs in handling BP vs smokeless is because of their different ignition & burn charateristics. Also I believe BP is classified as an explosive & smokeless as a propellant. BP is easier to ignite & burns at essentially the same speed in the open as confined. Take just a dab of each & pour out on a smooth hard surface & ignite each with a match, the difference will be immediately apparent. I "Found this out for myself" years before I had even heard of Bell. As long as kept dry BP will burn effectively at any level one might desire to load in a gun, from the max load on down. Smokeless on the other hand requires a minimum pressure level for insured ignition. Many I fear are taking powders out of their design parameters in the desire for extremely low pressures & are courting with failure, perhaps a load left in the bore which could be disastrous if undetected.

That's the graph I have saved. I just don't know how to post it.
Thank you, Pete.

You'd have to have a holy man lay hands on a gun that came out of the blackpowder period to know if the ol' bitty was safe enough.
Its not black v smokeless, its what the old toads and their sons stuffed in it all those years before it came to your cabinet.
A gun is a gun, and stout loads were the thing.