Dear Ranch13;
I am sorry to learn that you are still befuddled. I am doing my level best to unfuddle you. Let's take your questions and observations point by point.
Despite your assertion that I am unwilling to accept findings from different sources, I am perfectly willing to accept such findings. Haven't I been requesting that folks tell me of any information they might know of concerning BP cartridge pressures, including pressures measured with strain gauge setups?
You ask have I, "Noticed by now that no two outfits data will completely agree." Yes, of course. That was the whole point of my initial request for information and of all the ensuing discussion. The BP cartridge pressure data provided by Accurate, Lyman, and Spencer Wolfe differs by at least 10%. While this is pretty close, the data from the different outfits obviously does not completely agree. Probably, if it all agreed, we would not even be having this discussion.
You wrote, "Until now you have said little if anything that I've seen about how you 'worked' into that almost suicidal charge."
There are two points here: my research method, and the alleged suicidal nature of the 40-82 charge. I apologize if I had not made my research method clear to you in my initial posts. I did not realize it would become such a bone of contention. The use of graduated charges and close observation for undue pressure signs seemed like such an obvious protocol that I did not explain it in detail in the initial posts. Clearly, the use of graduated charges and modern bolt action rifles capable of containing 150,000 psi of pressure or more was completely safe when considering a charge whose maximum pressure could not exceed 86,000 psi. Just compare the numbers.
Regarding the 'suicidal' nature of the 40-82 charge, it may seem like splitting hairs, but the problem there was not the charge of 4Fg. It was the cartridge case length. As noted in an earlier post, that particular cartridge would probably have generated similarly high pressures if I had loaded it with 2Fg or 3Fg. If a bullet is trapped in the case by a case mouth crimped into the throat, the propellant gases have nowhere to go and pressure builds in the chamber. Fortunately, with BP you are limited to a maximum pressure of 86,000 psi. Hence firing such a cartridge in a suitably strong firearm should not be construed as evidence of suicidal proclivities. If the firearm can safely contain 150,000 psi, a load of 86,000 psi should not be fatal to anyone standing behind the muzzle.
You wrote, "You also let on that you've well versed in reloading. It seems to me that you would know that a case that was a little long isn't to likely to pop primer pockets, unless you were already way over the top on pressure. Also I suspect you had to fire that charge or something similar multiple times to get a 40-82 case to stretch enough that it could become dangerous."
It's true that I'd had a lot of handloading experience prior to that 40-82 overpressure incident. But most of that was with smokeless, and I was still learning the quirks of BP. BP is different from smokeless in several respects. One is its proclivity for causing case stretching, especially in new cases. Unlike the rounded grains of smokeless, grains of BP tend to be more sharp cornered. When BP is fired, the forward part of the powder charge is temporarily compressed and squeezed outwards against the case walls. Those sharp cornered BP grains press into the wall of the case, especially near the neck, and as they are propelled forwards they tend to drag the case along and stretch it towards the throat.
This phenomenon is more common in the longer express cases like the 40-82. Older cases which are work hardened are less susceptible to such neck stretching than new cases. Older cases stretch more near the base. When I did that series of 4Fg experiments 10 yeas ago, I was using new cases. Stretching a primer pocket in a solid headed rimmed case requires a lot of pressure, right up near the 86,000 psi maximum that can be generated with BP.
You wrote, "It could of been that that case stretched as well as blew the primer with that dangerous overload you had stuffed into it."
Well, anything is possible, but BP is noted for its consistency of ignition. That's why we can get such low SDs in our muzzle velocities. Remember, that load of 82 grains of 4Fg was not inherently dangerous in that situation because it could not generate more than 86,000 psi and it was being fired in a modern rifle that could easily contain 150,000 psi.
Before firing the 40-82 which over stretched in the chamber, I'd fired four other 40-82s with the same load of 4Fg, all without any signs of excessive pressure. Recall, I was using the CCI pistol primers whose thin cups were then reputed to show pressure signs at just 35,000 psi. I'd fired five rounds of 45-70-500 4Fg with no adverse pressure signs. I'd fired five rounds of 38-90 4Fg (375 H&H) with no adverse pressure signs. I'd fired four rounds of 40-82 4Fg with no adverse pressure signs.
Then, on the fifth round of 40-82, the primer pocket was loosened and the muzzle velocity jumped 100 fps. When that cartridge case was extracted, the case had lengthened and the case mouth had tapered in as if it had been crimped. But I had been loading without any crimp. None of the other fired 40-82 cases showed any tapering of the case mouth. All those other cartridge cases were still of normal length.
It seems to me that, if fourteen cartridges had been fired without any signs of overpressure or case mouth tapering, and then one cartridge with an identical load showed an increased length, a tapered case mouth, and a dramatic overpressure, the previous fourteen loads were probably not dangerous, and something other than the amount or granulation of the powder was responsible for the excessive pressure of the fifteenth round.
You wrote, "As I've said before that you didn't lose any body parts is certainly a testiment to the quality of that Csharps."
Yes, the C. Sharps 1875 action is very strong, probably at least as strong as a Winchester Highwall. That's one of the reasons why I felt it safe to fire a cartridge that could potentially generate as much pressure as 86,000 psi. I certainly would not have wanted to fire such cartridge in a Ballard or a Stevens 44 or a Maynard. Even a replica made of modern steel could be unsafe at this pressure if the action design is weak. I recall, when Red Willow first introduced their Ballard replicas, I asked one of their guys about the strength of the new actions. He said they were very strong. He said they had chambered one in 44 Magnum and fired a proof load. He said the barrel and the receiver did not burst, but the breech block did bend. Frankly, this is not my idea of a strong action.
You wrote, "I also can't understand why you won't take SAAMI's pressure specs on cartridges as proof of how much pressure blackpowder and cartridges generate. The 45-70 (Trapdoor) is set at 28000 psi, I would expect that's probably what would be when loaded with a 500 gr bullet and 70 grs of 3ff. 2f loads will likely be a bit less, another example is the 38-55 it specs at 30,000 cup."
I'm happy to accept SAAMI specs as the maximum pressure allowable for black powder arms. But a SAAMI spec is not necessarily based on the maximum pressure anticipated with BP. I don't know what data SAAMI's 38-55 pressure limit of 30,000 psi is based on, but I suspect it must be a later high speed smokeless load intended for the Winchester 1894. It seems unlikely that 55 grains of 3Fg and a 330 grain bullet could produce 30,000 psi.
We can agree that SAAMI's 45-70 max. of 28,000 psi is probably based on a 70 grain load of 3Fg and a 500 gain bullet. The 45-70-500 3Fg is one of the few BP cartridges for which good, lab tested pressure information has been published. Spencer Wolfe wrote, "The M1881 bullet (500 grain) loaded with 70.0 grains of 3Fg gave a velocity of 1315 fps with an average pressure of 25,800 cup - 29,600 cup peak (per HP white labs). The Arsenal listed an average pressure of 25,000 psi for this load.... SAAMI gives the average maximum pressure for any cartridge fired in the 45-70 as 28,000 cup with 31,200 cup absolute individual peak."
Unfortunately, there are no SAAMI specs for many of the BP cartridges that we fire every day in competition. No one is saying that a 45 2 7/8 loaded with 2Fg is unsafe in a modern replica rifle, but it would still be nice to be able to estimate the amount of pressure being generated.
You wrote, "As the old Ideal manual stated it's hard to get into trouble when using the PROPER granulation of black powder."
True, but even here there is a difference of opinion about what is proper. Spencer Wolfe noted that different 19th century BP manufacturers used different standards for grading the size of BP grains. He says he made little progress duplicating the ballistic performance of Arsenal 45-70 rounds until he realized that the 1Fg referred to in the old records was the equivalent in grain size to today's GOEX 2Fg.
There's a lot about BP that used to be known but has been forgotten. Now we are testing and rediscovering stuff.
I am not bringing this information to your attention so that you will repeat my overpressure experience. I want people to avoid 4Fg as a primary charge in BP cartridges. I am discussing this matter as a cautionary tale.
I do not condone the use of 4Fg as the primary charge in BP cartridges.
Besides the risk of the unknown, there are some practical considerations. Successful BP bullets require a moderately soft alloy to cope with bore irregularities caused by fouling. The pressures generated by 4Fg are higher than 2Fg and 3Fg and therefore require harder alloys or shorter bullet noses to prevent nose slumping and inaccuracy. I believe that any slight velocity advantage that might be obtained with 4Fg is more than offset by the blunt nosed, high drag bullets that must be employed with it and the necessary use of hard alloys which cope poorly with BP fouling.
Ranch13, I apologize for going on at such length, but your persistence in asking these questions and making these observations indicates that you have a genuine desire to understand this stuff. Therefore it only seemed right to address your questions and observations in a point by point manner. Thank you for your continuing interest in this topic.
To conclude, I'm looking for lab tested data on pressure generated by BP cartridge rifles. Can anyone help with this search?
All the best,
Dick Gunn
