Calculating black powder pressure, caliber, steel and wall thickness

# Thread: Calculating black powder pressure, caliber, steel and wall thickness

1. Plastic
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## Calculating black powder pressure, caliber, steel and wall thickness

Does the ”honeycomb” construction of a revolver cylinder make it stronger compared to a single barrel? The reason why I’m ask is because I’m trying to figure out the minimum safe wall thickness for a single shot black powder pistol. The pistol I’m making will be loaded with a patched .53 roundball (weight 231 grains) and the maximum charge I’ll ever use behind that roundball is 80 grains of pyrodex P (FFFG). In which maximum pressure range will such a load be within? It’s hard to find pressure values on black powders loads, however it seem to me that black powder is in most cases low pressure compared to smokeless. In comparison, will the load I’m using have higher or lower pressure compared to the pressure generated by a 28 gauge modern shotgun?

According to this resource https://www.cip-bobp.org/homologatio...s/a-4-1-en.pdf the minimum wall thickness at the chamber area for a 28 gauge shotgun is 1.05mm of the best steel, and 1.9mm if you use the weakest steel that’s included in the list. With black powder, where does the pressure peak? In a black powder revolver, does the pressure peak in the cylinder or in the barrel?

2. Titanium
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Why is it hard to find pressure details?.....The Lyman BlackPowder Handbook is full of them.....in any case ,Its virtually impossible to exceed 10kpsi with BP ,so if you work on that you cant go far wrong.............I also think your projected charge is excessive ,and will do no more than produce a massive muzzle flash and cloud of smoke .....anyhoo ,you can experiment with that.....You should note that thin walls may sustain mechanical damage ....ie denting........The only 58 cal revolvers Ive ever heard of were the old Webley Pryse and Webley No 1,and the balls travelled so slowly that the shooter could see them in flight........I think Tranter may have sold a 58 revolver too.Most of these guns were Belgian in origin,and Ive read that Pryse and Redman was just an English sounding name dreamed up by the Belgians ,who invented the Pryse locking system for break top revolvers. .

3. Diamond
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john k

It appears you are well versed in BP.

Can you comment on the differences that might be observed when FFg is used as a replacement for FFFg grains of any commercial BP?

Other than unburned grains left in the bore with resultant effective light loads when using the coarser grains, I can not get a picture of the difference. Note, I'm just starting out with BP for the back yard fun of smoke and noise. Italian made replica Army model revolver and a carbine with percussion ignition.

4. Its virtually impossible to exceed 10kpsi with BP
Which is more than enough to destroy poor metallurgy

THE FORGOTTEN TRAGEDY The 1844 explosion on the USS Princeton shook the presidency of John Tyler | Town And Countymiscellaneous | fredericksburg.com

15" Naval gun explosion 1844

5. Diamond
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I;m gonna be real keerfil loadin that 15 incher in the back yard from now on. a ex-ploshin like that might scare the chikens an the pigs.

6. Titanium
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Im not quite correct...the first blackpowder rounds for the new 303 generated 19 tons per sq inch,but to achieve that they crammed 71 grains of powder in a 303 case,loose powder ,doubtfull if youd get 50 grains in......Another gun where there were optional black and smokeless loads was the British 6" naval gun of the 1890s,either 12lbs of cordite or 28 lbs of blackpowder produced 2000 fps with the same projectile.In 1943,a warning shot from one of the old 6" guns on Moreton Is struck a Dutch minesweeper,and despite being a dummy shell containing gypsum powder,it killed five men on the Dutch boat.

7. Diamond
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Originally Posted by john.k
Im not quite correct...the first blackpowder rounds for the new 303 generated 19 tons per sq inch,but to achieve that they crammed 71 grains of powder in a 303 case,loose powder ,doubtfull if youd get 50 grains in......Another gun where there were optional black and smokeless loads was the British 6" naval gun of the 1890s,either 12lbs of cordite or 28 lbs of blackpowder produced 2000 fps with the same projectile.In 1943,a warning shot from one of the old 6" guns on Moreton Is struck a Dutch minesweeper,and despite being a dummy shell containing gypsum powder,it killed five men on the Dutch boat.
Do you know of anyone who actually shoots small caliber BP that might have an idea about FFg vs FFFg?

8. Titanium
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Yes,FFFg will produce a bit more velocity ,and a bit more fouling than FFg,generally.....In a C&B revolver ,charge is limited by the bullet ,you can get a bit more in the cylinder with roundballs,conicals take up more space......Ive found that 2&3 Fg can be used just about interchangeably in a longarm ,a revolver is better off with 3Fg,smaller calibers like 32 ,4F is ok....The secret with any blackpowder gun is to use the right lube and plenty of it....a good blackpowder lube is olive oil and beeswax,50/50.....or just straight bees wax was also used in big rifle cartridges,in the form of a 1/4" thick disc under the bullet.

9. Aluminum
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I would personally use FFg over FFFg, it changes the burn rate and speed due to the size. you want it to push the projectile out the barrel without a massive pressure spike with a super fast burning powder

10. One time I was shooting my .33 caliber rifle with a 37" barrel at a muzzle loading range and a more experienced shooter asked what grain powder I was using. He said the FFG was too slow burning and not getting full velocity. He put in a load of the FFFG he was using in a pistol and I started getting loud cracks, indicating it was over 1000 FPS.

Bill

11. Titanium
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When you get sonic cracks ,vel is likley well over 1150f/s,usually somewhere around 1250f/s.Its good when the hiss changes to a crack,but the noise does nothing for accuracy,the trans sonic zone being notable for buffeting of the bullet.

12. Diamond
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Here is a link to someone's previous work on the topic.

Black Powder Pressure Curves & Bullet Obturation

I can't say a thing about it, but...Interesting.

13. Titanium
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Not really informative,because he lumps all "smokeless" into one (IMR4759),and as we know,smokeless runs the gamut of rates from Norma R1,faster than Bullseye,all the way to cannon powders,which wont burn in a rifle sized case.......The local manufacturer states that their smokeless Trailboss powder is the same rate of pressure rise as Black ,and furthermore states that blackpowder is a bit slower ,pressure rise wise,than Bullseye.Although various researchers and shooters with pressure measuring equipment dispute this statement.(That Trailboss equates to Black)..............Warning......never use any nitro powder,not even TB,in a muzzleloader,

14. Diamond
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Originally Posted by john.k
Not really informative,because he lumps all "smokeless" into one (IMR4759),and as we know,smokeless runs the gamut of rates from Norma R1,faster than Bullseye,all the way to cannon powders,which wont burn in a rifle sized case.......The local manufacturer states that their smokeless Trailboss powder is the same rate of pressure rise as Black ,and furthermore states that blackpowder is a bit slower ,pressure rise wise,than Bullseye.Although various researchers and shooters with pressure measuring equipment dispute this statement.(That Trailboss equates to Black)..............Warning......never use any nitro powder,not even TB,in a muzzleloader,
I didn't think it was a comment on smokeless, except for that single type used in comparison. The text is the meat and potato!

Pressure rise 2X to 5X faster over smokeless.....

NOTE ALSO! The writer is in to BP Cartridge rounds. Loads in brass cases with center fire primer ignition.

eta

I have heard of some BP shooters sprinkling a pinch of smokeless in prior to dumping in the main BP charge....' Secret mix?

Pertinent info:

You'll notice that the Goex rise times are essentially twice as fast as
the IMR4759 rise times. I’ve seen numerous pressure curves of various
smokeless ammo rifle loads and typical rise times were in the range of
180µs to as much as 400µs. So there should be no doubt that the burn
rate of black powder is significantly faster than smokeless, although
not by an order of magnitude but rather by factors ranging from 2 to
5.

Also note that the three BP types ALL resulted in HIGHER pressures than did the smokeless comparison,

Tell me. what is the mechanism that makes smokeless powders unsuitable for percussion cap applications?

Operator error that puts 80 grains of smokeless where 20 would be more correct?

15. Titanium
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One of the complaints I hear about Trailboss is the rate of pressure rise is a lot faster than black powder...........the contention is this rapid rise equates to "gunbusting" ....which I have never found any evidence of ......the most recent instance of "busted gun" I ve seen related to a low load of Unique,and IMHO ,opened up a forging defect in a Martini action made in 1874.....So Trailboss cant be blamed for that one.