Has anyone got access to real BP pressure data ?

[MEHavey]

There's an awful lot of "as reported on the internet" and hand-drawn pictures out there.
And an absolutely incredible amount of "...it's well-known..." knowledge.
But does anyone have real data comparing BP v Smokeless pressure curves in BPCR cartridges?

Driftwood Johnson's Post in three years ago and TexMac http://www.texas-mac.com/Black_Powder_Pressure_Curves_and_Bullet_Obturation.html begin to address. Taken together the two articles begin to tackle the screaming & yelling matches that go on about what's best for bullet obturation to seal the barrel for cast loads.

I maintain that a fast smokeless powder is far more effective in "upsetting" the cast lead projectile in that regard, when compared to BP. Others take almost a religious zeal in claiming that it's "well known" [aka settled science] that BP gives the fastest "bang" as an explosive. (and then they cite burning powder trails of BP vs smokeless on one's open-air driveway as to the "burn speed" advantages of BP -- which is of course irrelevant.)

While directly applicable to relative risetimes, the texas-mac article limits the discussion to SR4759 -- which was deliberately developed to have pressure risetimes akin to BP. Others state that while smokeless does rise precipitously, "black powder beats it out at the start."

I think Driftwood's presentation puts that in perspective. The key is "equal outcome" -- projectile velocity when exiting the barrel.

https://www.thehighroad.org/index.p...d-effects-on-guns.829596/page-2#post-10703480

(A well-worn image, but one directly applicable to the kind of ballistics of many heavy BCPR cartridges w/ cast bullets)

Since that velocity is a function of work done on the bullet, and that total work is a function of area under the pressure-time curve, the lower/slower BP curve produces the same velocity and rolls over onto peak, and off of peak, at far lower peak than smokeless -- FAR lower.

Meanwhile, the smokeless literally races past that BP peak, in about the same timeframe, to more than twice the pressure. A really sharp "punch" as opposed to a shove. (others will note the short/initial BP rise ahead of the smokeless very early in the game. But that poops out at very low pressures -- far lower than required to begin bullet/material deformation of even the softest alloys)

This is where I would submit that effective bullet upset/obturation occurs -- that sharp high-pressure punchwell above Brinell-derived deformation pressure of the alloy (BN*1,420 psi) -- and gives significant advantage to smokeless for cast bullet shooters.

Thoughts, rejections, additions.... ? better data ? better logic?

 

[Loyalist Dave]

This is where I would submit that effective bullet upset/obturation occurs -- that sharp high-pressure punchwell above Brinell-derived deformation pressure of the alloy (BN*1,420 psi) -- and gives significant advantage to smokeless for cast bullet shooters.

Thoughts, rejections, additions..

So I must have missed part of the point....,

I would have thought the rate of pressure increase likely inconsequential, so long as sufficient pressure was reached in sufficient time to obturate a conical bullet base onto the rifling.... the rest seems moot. Once sufficient obturation is achieved it matters little if one method on paper could cause 2X the obturation, or some other measure...

I don't understand the comparison..., Yes a sufficient smokeless powder charge would give a much higher pressure than a black powder charge, and would obturate a bullet base perhaps more than BP, BUT the vast majority of muzzle loading rifles do not use smokeless powder, nor can they.

Further, one would need to show that the obturation performed by smokeless powder on a muzzle loaded bullet was superior in accuracy to a sabot type bullet that was swaged directly onto the rifling when loaded. Otherwise why go to the trouble of making a smokeless powder powered muzzleloader? One reason why muzzle loader companies don't use steel comparable to modern rifles is that the softer steel used for the muzzle loader saves a great deal of money both in materials costs and machining costs.

Yes I've seen the "arguments" for the Firestick and the NitroFire, and the arguments for the Firestick are spurious, if not demonstrating a laughable ignorance about black powder (or maybe the manufacturer thinks the buying public are just plain stupid ? ) All it will take is for a legislative body to change the ML definition from, ".., and expels one projectile which was first loaded from the muzzle...," to something like, "..., and expels one projectile after the propellant and the same projectile were loaded from the muzzle..., " and the Firestick will suddenly become a weird breech loading rifle.

LD

 

[Dave T]

Loyalist, he said twice that he is talking about "black powder cartridge rifles", not muzzle loaders.

Havey, I'll offer two thoughts for your consideration.

First, a bullet only has to deform/obturate enough to engage the rifling and seal the bore from the powder gases. Black powder does that with the proper alloys. No further obturation needed.

Second, the choice between BP and Smokeless, at least in terms of safety, has to do with the age of the cartridge rifle. Modern made replicas of Sharps, Remingtons, and Winchesters (along with a few others) have the steel to easily handle reasonable smokeless loads. Older (original) BP cartridge rifles are made of steels that may or may not be up to that spike of smokeless powder. Or, repeated applications of that spike.

If you're talking about modern made guns the choice is yours. Either powder will obturate bullets of the proper alloy to shoot accurately. My personal take is, modern or original these guns and cartridges should be fired with black powder. Some things are just right!

Dave