Are there any charts on B.P. Cartidge Camber Pressure's?

[Ace Lungger]

howdy Folks,
I have been loading smokeless for many years, but just got into the B.P. last year. At some time I am going to put a new barrel on a Old Rifle converted to a shotgun action, I have allways wanted a 32-40. I am told that this action isn't real strong? So I want to put a caliber that has a low camber pressure with B.P., I have looked and have not found anything on B.P. chamber pressure's.
I would be great full for any and all help.
Thanks
ACE

[Pulp]

I can't think of any specific sites that you're looking for, but my poor little brain remembers something like around 10,000-12,000 psi.  But don't bet your rifle on that number.

The thing I do remember is the pressure curve for BP is much more gradual.  A smokeless load that hits 12,000psi usually hits it with a hard spike, and guns not rated for smokeless powder cannot tolerate that spike.

[Ace Lungger]

Thanks Pulp, I realy didn't want to go any smaller than that!
Thanks again!
ACE

[Short Knife Johnson]

I know a guy that has a .45-70 double rifle that is built on a shotgun action.  I don't know the particulars, but it works, and shoots fine.  With smokeless powder no less.  The barrels are independant of each other until about an inch from the muzzle.  I think this was to make fro easier regulating.  It was bought from a gunsmith in Saskatoon Saskatchewan who dug himself into a real financial hole with some chick and need to cash in his unique pieces.  Very cool gun, I wish I had it.

[john boy]

I have looked and have not found anything on B.P. chamber pressure's.

Here's the best you will only find ... http://www.assra.com/cgi-bin/yabb/YaBB.pl?num=1202959756/0

[Driftwood Johnson]

Howdy

Here is a pair of superimposed pressure curves that a retired ballistics technician sent me a few years ago. It may have been Old Scout, I don't really remember. These curves do not cover the caliber you are considering, but they are instructive anyway. As the title says, these are the curves resulting from two loads which each produced 1200 fps with a charge of 1 1/8 ounces of lead shot. Pressure is in psi, time is milliseconds.

The pressure curves of the two different loads are very different, despite the fact that the velocity and mass of the projectiles was the same. The Smokeless powder in question is not named, but whatever it was, there were 18 grains of it. What is impressive with this comparison is not just the fact that the Smokeless charge generated a much higher peak pressure, but the duration of the two different charges is also very interesting. The Smokeless peak is a sharp spike, rising and falling very rapidly. The BP pressure, in addition to being much lower in intensity, is also spread out over a greater amount of time, rising and falling much more slowly. Indeed, it is this rapid spike in pressure, in addition to the high maximum pressure that often results in the destruction of guns designed for Black Power. The old steel simply cannot take the shock of the sharp spike and shatters, whereas the longer duration of the BP curve is not so damaging. This is also why no matter how hard one tries to duplicate the pressure of a BP load with Smokeless, one cannot get away from the pressure spike, often leading to the destruction of old guns that one might have thought could withstand the lower pressure load.

The little spike at the far left of the BP curve is the primer, there is a hump in the Smokeless curve which was also the primer.

Not exactly what you were looking for, but instructive anyway.

[Pulp]

That's an interesting graph DJ.  I would have thought the BP pressure would have been higher than 4000psi.

[Short Knife Johnson]

There is a Mike Venturino article somewhere in my old Shooting Times from the late 90's where he put an Oehler strain guage on his Shiloh.  I'll have to try to find it.  I think his .45-70's were pushing 10,000 cup.  The pressure/time graph sure makes it easier to understand why a cast bullet obturates.  I try to explain to people at first that the projectile gets started with a greater acceleration than with smokeless.  Making it behave like a cartoon character out of Looney-Tunes.  They usually get it, but the odd one just doesn't buy it.  But I'll try to find that article.

[Dick Dastardly]

Howdy DJ,

That curve is right on the money.  I looked up the thread that JB mentioned and those graphs would fit the same curve.  Genuine black powder is quite well behaved if a few well established conventions are followed.

Given enough fools, nothing is foolproof.  But, black powder is about as close as you can get to foolproof for our mission.

DD-DLoS

[Lone Oak]

Pulp,
The bigger the bore, the more space there is and thus less "confinement" and so the pressure is lower, with black powder that is.
L.O.

[john boy]

But, black powder is about as close as you can get to foolproof for our mission.

Dick, an excellent statement.  Original gunpowder is a weak powder and as long as folks keep FFFFg flash pan powder out of their BP firearms as the main charge and adhere to the manufacturers recommended loading data, Fg to FFFg will keep them in the safe pressure curve.

What I do know is, for a 45-70 rifle the stated maximum pressure is 28,000 psi and the proof houses test at 35,000psi.  For BP handguns ... 

[Ace Lungger]

I want to thank everyone of you guys for all the advice! It all help, and I believe I have learned a big lesson in the reloading of Black Powder! I have heard a lot of people grip about the cleaning of a B.P. gun, but I don't mind that, what I do mind is cleaning the cases!

Thanks so very much!
Maybe someday I will be able to help some one!
Later
ACE

[Short Knife Johnson]

The ticket for cleaning cases is ceramic media, cleaning solution and a rotary tumbler.  As it happens, I'm picking one up this weekend.  I was shocked at the job they do.  The cruddiest cases look like new.  There are different sized media for different sizes of cartridges.  The most commonly used tumbler is the Thumbler.  The media and solution is available from several sources.  Shiloh Rifle in Big Timber for starters, but I'm just getting the whole deal from a guy I shoot with.  Just decap, put in solution and media, tumble for a while, and drain.  I guess the ceramic does not break down.  Whatever you lose down the sink is all.

[Trailrider]

Howdy, Pards,
Note that the pressure-time curves shown are for 12 ga shotgun, not metallic cartridges.  While there are similarities, we are still comparing at least Jonathan apples with Golden Delicious apples, if not apples and oranges.

While I'm not able to show the graphs here (unless somebody tells me how to do it), I DO have pressure-time curves taken on a .45-70 rifle using the Oehler M43 Personal Ballistics Lab, showing the curves of both Remington factory data and my own loads using cast bullets.  The smokeless powder P-T curves are much more gentle than produced by the 18 gr. charge shown on the other post.  Powders used were "Factory" (which looks suspiciously similar to IMR3031, and produced about the same results as similar charges of IMR3031 even though the factory powders ARE PROBABLY NOT the same.  With straight-sided cartridges, the trick is to use the slowest-burning smokeless that will ignite reliably, even if they burn a bit dirty.  I've had excellent results with IMR4198 WITH a FILLER, and IMR3031.  Some have even recommended IMR4831, though I've not tried that.

That shotgun load of 18 grains of whatever looks to be a fairly fast-burning powder, and I would expect a fairly sharp peak.  The burning rate of black powder is fairly fixed, whereas smokeless powders vary widely in burning rate.

I have a Navy Arms HiWall in .40-65 WCF.  There are no SAAMI specs for that cartridge.  IF I can find the time before the snow flies, I intend to cement a strain gage on the barrel and run some tests using VARGET powder and some others.  (Gluing strain gages on barrels is a fairly humongous pain in the "klarn"!)

If and when...I'll try to figure out how to post the data.  Meanwhile, stick with loads published in the various manuals!

[Jamie]

Going back to part of the original question - turning what I assume is a single or double barrel shotgun into a rifle - it certainly can and has been done.  I handled a Beretta double 12 that had had the monobloc sleeved with 45/70 barrels, and the individual shot moderate smokeless loads through it - the gun was featured in a Gun Digest "One good gun" article, though the year escapes me.  The owner of the gun and author of the article was Clayton Williams of Dansville NY.  In addition, I believe that it was CZ that produced (still does?) a quasi-side hammer double (the external "hammers" cock the internal firing pin springs) for which you could purchase separate full length inserts that fit tightly at the chamber, and were secured at the muzzle by special inserts which used the choke tube threads.  Aside from the fact that the gun wasn't particularly attractive - a pretty well thought out process.  I have never talked to anyone who shot one, so I haven't a clue how they actually worked.  In addition, H+R or New England firearms makes, as you are aware, I'm sure, rifles on their single shot action up to and including pressure levels of the 25-06.  I don't know if they are somewhat beefed up versions of the same action used for the shotguns, but from what I understand, you can send in a rifle receiver and have a shotgun barrel fitted to it, or any other rifle barrel that they make, but you can't send in a shotgun receiver and have a rifle barrel put in place.  I

In a conversion like you're talking about it seems to me that the key is the condition of the action and it's original strength, as not all guns are created equal, and steel varied dramatically, especially way back when.  Check the action through a gunsmith, they CAN tighten things up, though from what I understand, that can be an expensive process.  I had a friend who quit shooting his Perazzi trap grade over/under which he bought new because it started opening up on him.  Mind you this guy shot trap competitively and had put over 100,000 loads through that gun. 

At any rate, with what you're contemplating, especially with black powder, the quality and condition of the action would seem to be the crucial issues, as a good action should definately be able to get the job done.

Jamie 

[Ace Lungger]

Thanks Jamie,
The action on the gun is great. I just don't know the strenght of the steel. I was going to put on a 45-70 barrel and put my 22 insert into it and have fun! but the barrel came out of the tube and I ended up with a empty tube, the guy that shipped it to me didn't put any INS., so that is just a loss!
Thanks for the help!
ACE

[French Jack]

The Brits proved many years ago that BP could approach pressures of 100k.  I don't remember the specifics, but the geometery of the chamber to bore was part of the equation.  Thus, it is pretty good practice to stick with either straight or moderately tapered/bottlenecked cases.  Test results from Springfield in the 1800's showed no velocity gain past a point that could be obtained with straight walled cases, but pressures were much higher in bottleneck cases with same powder charge. 

The higher pressures are very likely the reason bottleneck cases are usually known to produce harder fouling in the bore with BP.

[Short Knife Johnson]

Check out Paul Mattew's Book Shooting Black Powder Cartridge Rifles.  He's got a section in there where somebody had taken a Rolling Block .45-70 up to 135,000 cup or something like that, and the load that blew the action up was way higher than that.  I'll dig up my copy and get the particulars.

[Jamie]

Dear Ace,
OK, I just read your "Buffalo Rifles" thread on the rolling block you put together, and as you knew when you replied to my earlier comments on this thread, you already knew way more than I did!  Thanks for being kind and not saying something like, "Yeah little feller, I already knows that stuff!"   Again, your kindness at my ramblings is appreciated!  I did look up some black powder ballistics in a couple old Gun Digests, but they were muzzleloader information, and as has already been noted, the difference between pressures in shotgun, brass cartridge, and muzzleloaders can be pretty substantial from what I gather, so that info wouldn't be too helpful either.  Oh well.  Anyway, keep us posted on the progress.  I've often thought about the possibility of making a caplock .32 barrel to slide into one of my old sewer pipe barreled Stevens Favorites, but I'm not sure that the barrel thickness once turned down to fit in the action would be adequate, not to mention the question of a firing pin alteration.  Have you ever played with one of them?  The other thought would be to turn it into a black powder only .32 Smith and Wesson, and the question of whether or not, if it could be done, would I need to stick to shorts, longs, or, again, with exclusively black powder, could I actually use the .32 H+R magnum case?  So I've been following this thread with great interest.  Anyway, thanks again for your kindness
Jamie

[Ace Lungger]

Howdy Jamie,
I don't know very much about Black Powder! What I have learned is what a friend of mine that has been shooting B.P. for 20 years, and what I have ask here, the pards on here are good to help people like me. A friend of mine give me a Trap Door Barrel, and I am going to put a 22LR barrel liner in it. It won't been as fun to shoot, but I know that it will be safe.
Thanks everyone!
ACE