doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Black powder and service pressures.

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.

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.

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.

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?

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.

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.

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.

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.

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

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.

Here 'ya go Keith, since you "have no exact dates (sic - data?) at hand right now" and apparently couldn't find the time to locate it.

Sporting Guns and Gunpowders: Comprising a Selection from Reports of Experiments, and Other Articles Published in the “Field” Newspaper, Relative to Firearms and Explosives, 1897
http://books.google.com/books?id=inQCAAAAYAAJ
“Powder Pressures At Different Parts of the Gunbarrel”, 1895
https://books.google.com/books?id=inQCAAAAYAAJ&pg=PA32&dq

Black Powder Pressures for a service load of 3 Dram Eq. with 1 1/8 oz. #6 shot at 1220 fps



72 gr. C&H No. 2 T.S. (somewhat similar to FFFg) = 3.2 Tons = 9,632 psi (converted using Burrard's formula)
84 gr. C&H No. 6 T.S. (similar to Fg) = 2.1 Tons = 5,936 psi
82 Gr Curtis & Harvey’s No. 4 T.S. (similar to FFg)
Breech - 2.26 Tons = 6474 psi
2 1/2" - 1.96 Tons = 5466 psi
6” - 1.26 Tons = 3114 psi
12” - .9 Tons = 1904 psi
18” - .37 Tons
24” - .27 Tons



And as jones said, the British Proof House made no mention of service pressure until 1925; when the 12g barrel flats were marked with chamber length and 1 1/8 or 1 1/4 oz.
The 2 1/2” & 2 5/8” 12g maximum service load was reduced to 3 Dr. Eq. with 1 1/8 oz. shot with a mean pressure of 3 1/4 tons by LUP = 9,800 psi by Burrard’s conversion.
The 2 3/4” 12g max. service load was 3 3/8 Dr. Eq. with 1 1/4 oz. shot with a mean pressure of 3 1/2 tons = 10,640 psi by Burrard’s conversion.

I "have no exact dates or data" as to Black Powder proof after the 1925 revisions and since, but hopefully Keith will post his research.

For those with the interest, the last article in John Brindle's series in The Double Gun Journal, “Black Powder & Smokeless, Damascus & Steel” was in Volume 5, Issue 3, Autumn, 1994, “Some Modern Fallacies Part 5”. He discusses in detail the progression of black and smokeless proof, but has very few pressure numbers.
This is one of his conclusions:
"The pressures produced in the breechloader by black powder, as black powder was actually loaded at the end of the 19th century, were not significantly lower than those given by smokeless (then often termed “semi-smokeless”) powders developed as a substitute for, and an improvement on, black powder."

Our local library obtained a PDF copy of the entire series for me in 2016, but it is under copyright by DGJ so I can't share it.

Preacher, I'm not sure why Dave has not yet approved my earlier reply to you, yet approved my replies to MC and SKB. I don't think it was any more vicious or mean than this recent reply you made to ED.


And I thought that reply to Ed was pretty funny, considering all of the times you have played the victim here... such as when Conservative commentary pushed you over the edge, and you posted this emotional farewell... but didn't really leave, and continued to log in, read replies, and even make replies:

https://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=456891&page=1

Of course there have been other times you played the victim, and did things like posting pics of your dead dog and little Guatemalan kids to gin-up sympathy.

That stuff about your supposed medical profession ethics was precious too. You have frequently made medical psychological diagnosis right here, over the internet, without ever personally examining the patient. And I do not believe that you are a licensed Psychiatrist or Psychologist either... are you? And even when it comes to being a Preacher, you falsely accused me of proof texting scripture, yet ignored repeated my requests to show us exactly how or where I did that. I'm still waiting... but we both know your real intent was to make me look bad, and yourself virtuous... which is simply hilarious.

And note this well, I never said that I would actually return with data or dates concerning the inception of accurate pressure measurement in guns by Ballisticians and Proof Houses. My reply to Shotgunjones was intended to give him something factual to consider, and my final statement there was intended to trigger a copy-and-paste wannabe shotgun expert into revealing himself. Mission accomplished.