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KY Jon Offline OP
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Looking at a Black powder proofed gun, 2 3/4” chambers, reproofed in 1980, trying to figure out what the service pressures should be? Or are all Black proof guns to be considered the same if 2 1/2” or 2 3/4” with service pressures in the 5,000 range? After 30 plus years I finally have a basic standard pressure load range for Nitro. Black powder pressures are the last piece of the puzzle. So what is the general answer.

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KY Jon Offline OP
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So I spent five hours reading everything I could about Blackpowder pressure levels for period ammo. I was hoping for a straight forwards answer like service pressures for modern nitro proofed guns but none seem clearly defined. There is a lot out there, but much of it has little fact basis. Just the usual Damascus is unsafe to shoot rants and Black will eat your barrels myth. From what I see the default period service pressure is in the 5-6,000 psi range. There are examples under 5,000 but just as many or more above.

The goal is a safe, sane, nitro for Black load. My default Black powder pressure point looks to be in the 5,00-6,000 psi. Out of concern for the wood velocity will be under 1150 more towards 1050-1100 FPS and payload of one ounce or less. Pattern boards will help decide what loads seem best. Glad I have 30+ pounds of PB and several pounds of other discontinued powders to work with. I have a Westley Richards, Bar in Wood, hammergun double which ought to be a fine dove gun this weekend if I get the shells loaded. Off to the loading bench.

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I'm of no help Jon regarding 1980 BP proof.

I can tell you that 82 Gr. (3 Drams) of Curtis & Harvey’s No. 4 T.S. (similar but not equivalent to to FFg) with 1 1/8 oz. shot (at 1222 fps) had a breech pressure of 5,820 psi in one report and 6,474 psi in another. Hall & Son No. 4 was similar.
1 1/4 oz. with 3 1/4 Dram No. 4 TS had a breech pressure of 7,790 psi
Definitive Proof under the 1896 Rules of Proof was with 6 1/2 Drams Proof-House Black Powder with 1 2/3 oz. No. 6 shot with a pressure of 10,100 psi.
That same charge of No. 4 TS had a pressure of 16,150 psi.

Those pressures were measured using crushers (LUP) and reported in pounds/ sq. inch; modern piezoelectric transducer pressures would be 10 - 14% higher.

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At the risk of stating the obvious have you seen Ross Siefried’s recent article on black powder and nitro for back shotgun loads in the summer 2021 DGJ?

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KY Jon Offline OP
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I did. One of about 30 articles I read today. What I was after was Black Powder service pressures not just safe Black or nitro for Black loads. There are several excellent articles and extracts from The internet on this plus Drew has assembled a massive amount of period data. All well documented by the way.

But I still have not seen a direct standard service pressure for Black powder. For Nitro 850 bars or 1200 bars, 2 1/2, 3, 3 1/2 & 4 tons there are clearly recommended service pressures expressed in bars and psi. Perhaps none exist because pressures on Black were pesio or LUPs and never directly measured in bars , tons or psi. There are formulas to convert LUP o PSI but they just give you an approximate value. Since Black is still offered as a lesser Proof these days there is no great demand for it I’m sure other than for guns which are deemed not like to to pass modern Nitro proof.

One article used a 200% Proof which correlates with a 3 1/4 dram (standard) being proofed at 6 1/2 drams. But the proof pressure is not a linear curve and just taking 1/2 proof pressure as your service pressure could be just a WAG. Most likely that is as close to an answer as I will get.

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I think you're looking for something that was not published or documented because it was not needed or even thought of at the time Jon.

The need for 'service pressure' standards arose with the development of smokeless powder.

With black, you charge by weight and what you get is what you get. Thus, the '3 dram' load.

Certainly different powders would develop slightly different pressure, but with a 200% overload being 'proof' whatever variation there is would be moot.


"The price of good shotgunnery is constant practice" - Fred Kimble
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Originally Posted by Shotgunjones
I think you're looking for something that was not published or documented because it was not needed or even thought of at the time Jon.

The need for 'service pressure' standards arose with the development of smokeless powder.

With black, you charge by weight and what you get is what you get. Thus, the '3 dram' load.

Jones, I have no exact dates at hand right now, but I'm sure you'll find that ballisticians and proof houses had pretty accurate means of measuring peak pressures before smokeless powder came into common use. In fact, they were measuring pressures at various points along the length of gun barrels, and plotting pressure curves. This information helped gunmakers design and build barrels with adequate wall thickness to withstand firing without failure, and with a built in safety margin without excess weight.. But I'll bet you knew this because we have discussed ballistics, and I know you are hardly a novice in these matters.

If I get time later, I'll try to copy and paste some history of pressure measurement so I can pretend to be a shotgun expert... or I can just smile about raising someone's blood pressure to aneurysm popping level. cool


A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.

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KY Jon Offline OP
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Shotgunjones I think you are exactly right. So we have to just base it on what pressures we can determine Black powder shells of the day would generate. Thanks to Drew there are several different known Black powder pressure loads from the period and from that I think a basic load of 5-6,000 psi is going to be my safe pressure load. In fact I loaded 50 tonight for Dove this Saturday. My 150 year old Westley Richards is going to get a workout along with my Lab of color.

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Originally Posted by KY Jon
I loaded 50 tonight for Dove this Saturday. My 150 year old Westley Richards is going to get a workout along with my Lab of color.

Without pics it didn't happen .............. laugh


"With one foot in the grave ..........and one foot on the pedal, I was born a Rebel" T.P.
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Originally Posted by keith
Jones, I have no exact dates at hand right now, but I'm sure you'll find that ballisticians and proof houses had pretty accurate means of measuring peak pressures before smokeless powder came into common use. In fact, they were measuring pressures at various points along the length of gun barrels, and plotting pressure curves. This information helped gunmakers design and build barrels with adequate wall thickness to withstand firing without failure, and with a built in safety margin without excess weight..

Even so, cartridges weren't loaded to a 'service pressure'. They acheived this only indirectly and the guns were designed to withstand the pressure from the commonly used loads.


"The price of good shotgunnery is constant practice" - Fred Kimble
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