Has anyone got access to real BP pressure curves ?

[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 [B]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.php?threads/bp-vs-smokeless-pressure-curve-and-effects-on-guns.829596/page-2#post-10703480
https://i.postimg.cc/FH90hYWF/pressure-curve.jpg
(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 punch well above Brinell-derived deformation pressure of the alloy (BN*1,420psi) -- and gives significant advantage to smokeless for cast bullet shooters.

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

[cas]

Maybe the black powder fouling just makes a better gasket. :)

[KenH]

That has been something I've asked about a couple of times and never got any straight answers. I'd LOVE to see a pressure graph of BP with a set size bullet, then similar pressure traces using same rifle, bullet, etc with several different smokeless powders, from fast to slow. I've been assured that QuickLoads gives decent approximate pressure graphs for smokeless powders. If so, all we need are some black powder pressure curves.

In the pressure graphs shown in the first link, under the right side of graph labeled as "est pressure", there is a column labeled "Peak" with values like "182", "209" and I'm not sure what that is. Should it be read as "18200 psi"? the last column listed as "Rise" I'm making the assumption that is the rise time in microseconds from time of 25% to 75% max pressure.

Thanks for starting the thread, let's see if any good answers are given.

[charlie b]

It would be nice to see the curves. Black powder is kind of a weird puppy. It has a really robust response to pressure that I do not think the shotgun data above fully explores.

The analytical work I did many decades ago showed a very sharp pressure spike with black powder. But, that was with burn rate info that was extrapolated from artillery stuff, so, results are not conclusive.

[dtknowles]

You know there is a guy on this forum that can do this. I think it would take a community effort to support this development but what a wonderful project it would

I am sure that Larry had a barrel instrumented in a 44 caliber cartridge that he could produce pressure traces for various propellants including BP and Subs and smokeless. This would be a wonderful project if we can provide Larry ammo to test.

If he can test 44-40 I woujld produce ammo for test but I may be wrong and only 44 special or 45 colt need apply. I will PM Larry if he does not respond.

Tim

[megasupermagnum]

You know there is a guy on this forum that can do this. I think it would take a community effort to support this development but what a wonderful project it would

I am sure that Larry had a barrel instrumented in a 44 caliber cartridge that he could produce pressure traces for various propellants including BP and Subs and smokeless. This would be a wonderful project if we can provide Larry ammo to test.

If he can test 44-40 I woujld produce ammo for test but I may be wrong and only 44 special or 45 colt need apply. I will PM Larry if he does not respond.

Tim

I'm 99% sure Larry has already done this. I seem to remember a comparison between FFFg and FFFFg in a pistol of some kind.

[KenH]

I remember Larry talking about doing some work on this but I was never able to find actual results. I suspect BP will give as much pressure as a properly chosen (NOT Bullseye, etc) smokeless at similar velocity.

I'd love for you to find the thread with the pistol BP curves. That would give some idea.

[Larry Gibson]

Yes, the above diagram is relatively correct as is your assumption; " This is where I would submit that effective bullet upset/obturation occurs -- that sharp high-pressure punch well above Brinell-derived deformation pressure of the alloy (BN*1,420psi) -- and gives significant advantage to smokeless for cast bullet shooters."

I can do a test specific to this question and would prefer to use the 45-70 cartridge?

[KenH]

Larry, I was hoping you'd chime in on this thread. A 45-70 would be perfect to test BP pressure curves vs smokeless pressure curve. Ideally I'd think both tests should be in the same rifle, same caliber, same bullet, with cartridges loaded for similar velocities.

I envy you with your pressure test equip. A good bit of money tied up in the equip, and time involved in testing. Thank you so much for your offer to test. Anything I can do to help just let me know.

Ken H>

[DonHowe]

I just load real black powder in cartridges for my back rifles. That is why I shoot back. I do not care about comparative pressure curves or which obituaries a bullet quicker. I fit the bullet to the barrel so obfuscation is not a factor. The whole point for me is to shoot the rifles and ctgs as they were 140 years ago.
Anyone is free to burn anything they choose but it ain't back if their is no bp involved.

[megasupermagnum]

I'm not sure which smokeless powders you guys use in 45-70, that is not a caliber I load. I did once read that bluedot has a curve very similar to FFg blackpowder, although I have no proof that it is true. I do see plenty shoot bluedot in 45-70. Just a thought.

[mehavey]

MANY thanks Larry.

I'm assuming any 405/535gr bullet w/ 65-60gr 2F/Sw1.5 (respectively) would be a rational 45-70 test object.

Again.... THANKS !

[Driver man]

I'll be following this thread with a great deal of interest.

[Larry Gibson]

Well a couple considerations. I only have GOEX FFg, FFFg and Cartridge. No one in this AO has any BP for sale that I know of. Obtaining other than those BPs may be a problem given the normal BP restrictions let alone the COVD situation.

For smokeless with the Lee 405 HB bullet cast of 16-1 or 20-1 alloy I suggest Unique, 2400, RL7, 3031 and 4895. I would hold velocity at 1300 fps +/-.

Name your poison....?

[mehavey]

GoEX 2Fg is not only fine, but probably most available/used.

*** CORRECTED FOR 24" BARREL ***

Running QL for a Lyman 405 / #457193(20-1) 415gr / 24" barrel
2400/20.0 gr/14,637psi - 1271 fps peak pressure at 670 microsec
RL-7/29.0gr/12,335psi - 1266 fps peak pressure at 750 microsec
3031/35gr/11,801psi - 1266 fps peak pressure at 650 microsec
4895/38gr/12,305 psi - 1277 fps peak pressure at 645 microsec

All estimates to get a ballpark (QL not liking straightwall, etc, etc
But in balance, probably the 2400 load for obturation test profile purposes

If you had it...
5744/24.0 gr/14,460 psi - 1284 fps peak pressure at 600 microsec

[KenH]

I'll second the choice of GOEX black powder with velocities in the 1300 fps range. My first thought was either FFg or FFFg, but thinking about it, sure would be nice to see FFg pressure compared to FFFg.

For Smokeless I agree that a fast powder like Unique would be good, as well as at least a mid burn rate RL7 and a slower powder like 3031. I know this is going to be lots of work for you and time consuming, and trying too many load combinations would be just too much.

Thank you again for the offer.

Ken H>

[mehavey]

Unfortunately, you can't even close to full-up 405gr/45-70/BP performance with Unique w/o approaching pressure limits.

But ... (for entertainment only/stronger actions)
Lyman 405 / #457193(20-1) 415gr / 24" barrel
UNIQUE/15.0gr/28,383 psi - 1,267fps peak pressure at 425 microsec (which is interesting)

Unique is doubly interesting at lower loads, however, precisely because it does run higher pressure/fast rise times for better bullet obturation

[Don Purcell]

Sherman Bell did a series of excellent articles in Doublegun and Single Shot Journal a few years ago on black powder and pressures with measuring equipment probably like Larry Gibson's. As for the speed of upset of the bullet William Ellis Metford proved back in the late 1800's that it was instantaneous before the bullet even moved. Metford did an incredible amount of experimenting and testing over at least a decade. The bullet metal he liked was very similar to our present day wheelweights. A very interesting person.

[mehavey]

Sherman Bell
See https://winchestercollector.org/forum/winchester-shooting-and-hunting/smokeless-versus-black-power/#p53575


For those of use w/ irritating Sharps 45-3¼s
https://www.castbulletengineering.com.au/downloads?download=9:finding-out-for-myself-express-rifle-case-fillers-by-sherman-bell-thanks-to-the-dgj

[KenH]

Those are some GREAT links. Thank you for them. Reading the first link I now understand why Larry suggested including 2400 powder in the test - reportley it gives pressure curve very similar to BP at the same velocity.

[KenH]

I don't wish to put any pressure on Larry for the tests, this post is just to keep the thread in everybody's mind and keep it from getting lost. This is a most interesting thread.

[mehavey]

Larry's probably waiting for a day that doesn't resemble an icebox.
:coffee:

[Larry Gibson]

Mostly, Larry needs to cast some bullets........

[charlie b]

And Lake Havasu City, AZ is not nearly an icebox :) He might have to wear something like long pants and shirts rather than shorts and sandals :)

[KenH]

Mostly, Larry needs to cast some bullets........
Larry, you just take your time and work at your own convenience. I'd be happy to cast up some bullets for you if wish. I've got the Lee 405 HB bullet mold you mention. I've got some pure lead and plenty of pewter (tin) to mix a 20-1 (or 16-1) mix. For a 16-1 mix, that would be around 8.6 oz of pewter to 8 lb of lead? Of course the % of tin in the pewter is the determining factor. I've read pewter can be from around 92% to 95% tin depending on the manuf.

Larry, I'll be happy to help. No point in you doing all the work, just tell me how many bullets you need shipped to you.

[Larry Gibson]

KenH

Appreciate the offer. PM sent.

[Larry Gibson]

Cast a couple hundred up this afternoon. Lee 405 HBs.

275517

[dtknowles]

Yes, the above diagram is relatively correct as is your assumption; " This is where I would submit that effective bullet upset/obturation occurs -- that sharp high-pressure punch well above Brinell-derived deformation pressure of the alloy (BN*1,420psi) -- and gives significant advantage to smokeless for cast bullet shooters."

I can do a test specific to this question and would prefer to use the 45-70 cartridge?

Look what I found, it is for 45-70 but is a bit cryptic.

275521

No units on pressure and no bullet weight but interesting anyway.

Tim

[KenH]

The pressure graphs look hand drawn, but the tables show pressures. Much like many have felt, BP actually gives higher peak pressures than a mid range smokeless powder like 4759. Looks like 4759 pressures are in the 15,500 to 16,500 psi range while FFg is 19,300 to 21,500 psi. I'm "assuming" those are for the same weight bullet and velocity, but that chart doesn't tell for sure. It will be really interesting to see what Larry's results are with his pressure equipment.

[dtknowles]

The pressure graphs look hand drawn, but the tables show pressures. Much like many have felt, BP actually gives higher peak pressures than a mid range smokeless powder like 4759. Looks like 4759 pressures are in the 15,500 to 16,500 psi range while FFg is 19,300 to 21,500 psi. I'm "assuming" those are for the same weight bullet and velocity, but that chart doesn't tell for sure. It will be really interesting to see what Larry's results are with his pressure equipment.

The charts have velocities and I am guessing you are suggesting that the reported pressures should be multiplied by 100. Few people explain their testing and data as well as Larry.

Tim

[crackers]

I thought this was settled back when the first guy blew up a BP barrel with nitro. 'Progressive burning' isn't a political statement.

[JSnover]

I thought this was settled back when the first guy blew up a BP barrel with nitro.

Come on, you know nothing's ever settled :)
I'd like to see the actual curves to compare the spikes and the timing and how quickly the pressure drops from the peak. Of course that'll only start more arguments but at least we'll have some good data.

[dtknowles]

I thought this was settled back when the first guy blew up a BP barrel with nitro. 'Progressive burning' isn't a political statement.

You can blow up a nitro barrel with smokeless powder. Back more than a century ago the factories loaded what were called Nitro for Black cartridges. What is settled is you can load nitro in black powder cartridge firearms but you have to know what you are doing. You should not be reloading anything if you don't know what you are doing.

Actually they don't call it Nitro for Black anymore but a bunch of factory ammo loaded with smokeless powder is loaded to low pressures so that it is safe to shoot in guns made before the switch to smokeless.

You might be talking about muzzleloaders but that is not what this thread is about.

Tim

[dtknowles]

Look what I found, it is for 45-70 but is a bit cryptic.

275521

No units on pressure and no bullet weight but interesting anyway.

Tim

I made a new graph with my best interpretations of that picture in my original post.

275562

Tim

[mehavey]

new graph with my best interpretationsJust so, Tim.
That spike is the BIGgest reason we tell folks to avoid TrailBoss is old/non-modern steel firearms.

[dtknowles]

Well a couple considerations. I only have GOEX FFg, FFFg and Cartridge. No one in this AO has any BP for sale that I know of. Obtaining other than those BPs may be a problem given the normal BP restrictions let alone the COVD situation.

For smokeless with the Lee 405 HB bullet cast of 16-1 or 20-1 alloy I suggest Unique, 2400, RL7, 3031 and 4895. I would hold velocity at 1300 fps +/-.

Name your poison....?

For Black Powder I would suggest Goex FFFG (I really don't think it matter much which PB you use) like is in the plot I made. Unique could be a stand in for Trail Boss, since it is the closest for burn rate. For the slower powder I don't know which to pick it is sort of a toss up but if I would have to pick it would be RL-7. I know that 2400 is a good choice but it is not enough different from Unique to prove/disprove the point.

Tim

[dtknowles]

Just so, Tim.
That spike is the BIGgest reason we tell folks to avoid TrailBoss is old/non-modern steel firearms.

Agreed but your point:

"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."

Would point to Trail Boss being very good for bullet upsetting and bullet obturation, just not good if you have a weak gun.

Tim

[mehavey]

Would point to Trail Boss being very good for bullet upsetting and bullet obturation, Yes. Correct.
In moderns guns.
(Which is where this whole thread started.)
:kidding:

[mehavey]

Unique could be a stand in for Trail Boss, since it is the closest for burn rate."Burn Rate" charts have gotten more people in more trouble than loose women. :groner:

"Burn Rate" is the speed of unpressurized powder.
It is only ONE factor in a powder's ballistic response:

- Burn Rate/sec
- Energy content (Heat/Kg)
- Ratio of specific heats (specific heat at constant pressure vs and the specific heat at constant volume)
- Progressive (or de-gressive) burning rate (with increasing pressure)
- Progressive burning limit (at which point it quits increasing pressure)
- ...and last but not least: a "Factor b" to balance the thermodynamics

As you can see, don't ever use simple Burn Rate to estimate loading results.

[Goofy]

275589

http://www.texas-mac.com/Black_Powder_Pressure_Curves_and_Bullet_Obturation .html

[dtknowles]

"Burn Rate" charts have gotten more people in more trouble than loose women. :groner:

"Burn Rate" is the speed of unpressurized powder.
It is only ONE factor in a powder's ballistic response:

- Burn Rate/sec
- Energy content (Heat/Kg)
- Ratio of specific heats (specific heat at constant pressure vs and the specific heat at constant volume)
- Progressive (or de-gressive) burning rate (with increasing pressure)
- Progressive burning limit (at which point it quits increasing pressure)
- ...and last but not least: a "Factor b" to balance the thermodynamics

As you can see, don't ever use simple Burn Rate to estimate loading results.

Are saying that you disagree and that Unique is not the powder that will most closely represent Trail Boss of those Larry suggested?

Tim

[mehavey]

- Delete -

[mehavey]

I am saying that published "Burn Rates" are near-meaningless when all the
factors affecting internal ballistics actually get going upon ignition in a cartridge

https://i.postimg.cc/vB8LyVwP/45-70-Trail-Boss-v-Unique-Trvl-sm.jpg
https://i.postimg.cc/NMh5ty93/45-70-Trail-Boss-v-Unique-Time-sm.jpg

[KenH]

275589
http://www.texas-mac.com/Black_Powder_Pressure_Curves_and_Bullet_Obturation .html
That is the best combining of those graphs I've seen. Thanks for posting - I'll really be glad when Larry gets his results posted so we can see some good graphs.

[KenH]

I am saying that published "Burn Rates" are near-meaningless when all the
factors affecting internal ballistics actually get going upon ignition in a cartridge
https://i.postimg.cc/vB8LyVwP/45-70-Trail-Boss-v-Unique-Trvl-sm.jpg
https://i.postimg.cc/NMh5ty93/45-70-Trail-Boss-v-Unique-Time-sm.jpg
A very good illustration showing difference in powders. That QL program is really great, as long as a person doesn't forget it's only a theoretical calculation and actual results might vary some, but it does get loading data in the ball park.

[mehavey]

Except for Fill volume, RED DOT acts more like TrailBoss in Max Pressure and Risetime.

In fact the curves overlay to the extent that I'd be almost tempted to say TrailBoss is
merely 'puffed' Red Dot (shot from guns, so to speak) :shock: :veryconfu




(But life can't possibly be that simple)
:bigsmyl2:

[dtknowles]

Except for Fill volume, RED DOT acts more like TrailBoss in Max Pressure and Risetime.

In fact the curves overlay to the extent that I'd be almost tempted to say TrailBoss is
merely 'puffed' Red Dot (shot from guns, so to speak) :shock: :veryconfu




(But life can't possibly be that simple)
:bigsmyl2:

Yeah but Larry did not offer to test with Red Dot.

Tim

[mehavey]

All I really want is the BP pressure/time curves. Data that
as far as I can tell either doesn't exist, or isn't available.

Everything else is gravy since I can then extrapolate from the
relative responses of the other powders he is going to test.

Not to worry.....

[dtknowles]

All I really want is the BP pressure/time curves. Data that
as far as I can tell either doesn't exist, or isn't available.

Everything else is gravy since I can then extrapolate from the
relative responses of the other powders he is going to test.

Not to worry.....

Post #40 had three black powder curves

[mehavey]

Without any units (other than apparent Peak Pressure), and without any related-
relative curves (other than "rise" which is/isn't 10-90% ?) with w/o anything but "Trailboss"

Which in earlier curves is shown to be (apparently) much Faster than BP.
(But that can't possibly be -- since BP is supposed to be faster than anything) :roll: :kidding:

Let's wait for Larry....

[dtknowles]

Without any units (other than apparent Peak Pressure), and without any related-
relative curves (other than "rise" which is/isn't 10-90% ?) with w/o anything but "Trailboss"

Which in earlier curves is shown to be (apparently) much Faster than BP.
(But that can't possibly be -- since BP is supposed to be faster than anything) :roll: :kidding:

Let's wait for Larry....

Are you kidding me about BP being faster than anything. Trail Boss is fast but not the fastest powder. Certainly there are smokeless powders that faster than BP but I don't think that Larry is testing with one that is. Unique might be a close match for FG but slower than FFFG. The next fastest powder he suggested 2400 is almost certianly slower than FFFG.

Another thing you mentioned is with smokeless the speed depends on conditions. If you limit smokeless to BP pressures they all get slower. Some will not even burn right at those low pressures.

Why won't your software make plots for BP?

Tim

[dtknowles]

Without any units (other than apparent Peak Pressure), and without any related-
relative curves (other than "rise" which is/isn't 10-90% ?) with w/o anything but "Trailboss"

Which in earlier curves is shown to be (apparently) much Faster than BP.
(But that can't possibly be -- since BP is supposed to be faster than anything) :roll: :kidding:

Let's wait for Larry....

The related curves are shown in the pictures, the plots are probably about 2 ms long since that is the likely barrel time. You can just drop a graph on them like I did in the comparison plot I made. I think they would be more accurate than the plots you posted from QL.

Tim

[Larry Gibson]

Take notice in drawn or, in particular, the computer generated traces they are nice and smooth with even curves going up and down. Many, if not most pressure traces, especially those at the low end of the 45-70 loads being discussed, are not smooth curves. So, if they are not smooth curves, as in illustrations, do not be surprised or assume something is "wrong".

Also, the computer generated curves and drawn curves are based on one input of data. What is will post will be the pressure traces and data of all the shots on each test. There you will see not only anomalies of each shot but the differences of each shot in a specific test of multiple sample shots.

[charlie b]

The trials of the test engineer. Trying to make sense of data that doesn't look like the models or theories :)

[mehavey]

What is will post will be the pressure traces and data of all the shots on each test.Exactamundo.
Real life is messy.

[Larry Gibson]

Got some bullets cast and loaded. Waiting for a "good" day of 65-70 degrees with acceptable wind to test.

275821

275822

[KenH]

We're all waiting with great interest in the results. Go Larry!!! Per NOAA it looks like you've got a few days of 50°F weather for a few days. BUT - you will get some decent days.

[charlie b]

I think your shoulder is going to be sore :)