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Old March 7, 2019, 04:13 PM   #26
prof marvel
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Join Date: March 9, 2011
Location: over the hills and far away
Posts: 31
My Good Thallub -

thank you for the civil and direct response!

I see you have read Bill's writings also

My personal experience differs from yours. from 1972 until the mid 1990's i used BP exclusively since it was readily available from several specialty shops as well as "over the blanket" at the several rondy's I attended . The worst BP I ever shot was a particular batch of Elephant that (after the fact) was acknowledged to be terrible at fouling. Bill opined that they , like Goex had gone cheap on the charcoal.

After the 1990's, BP became harder to get, and the number rondys in my area diminished. I started using Pyro, found it hard to ignite, and found the guild of professional builders who tested it extensively. As a result of that and the guilds findings of "chamber" erosion I decided to use Pyro only in firelocks that I could break down and clean very well, end-to-end. That way I saved my BP forcaplock and flintlock rifles, and I use Pyro in my revolvers and Sharps papercutter with a small BP booster. The other advantage to the Sharps is that I can fabricate and replace the chamber if I ever need to. (also, it's a cheaper italian copy)

Many, like yourself, believe this stuff is not "rocket science" . Yet, at the end of the 19th century, with the primitive tools available, ballisticians and chemists were making findings regarding gunpowder that seem to have been forgotten or ignored today.

For example:
- wavefronts.
It is well known that when gunpowder is ignited, the expanding gasses make a so-called "blast wave". what is less discussed is that the gun barrel acts as a pressure vessel with a rapidly expanding volume, and that gunpowder (and smokeless, I am sure) can and will under the correct conditions create high velocity reflecting wavefronts that travel back and forth and if multiple wavefronts coincide this can cause enourmous pressures. This was studied extensively in large Naval Guns but was demonstrated on a smaller scale in some small arms.

-burn rates and pressure
The "common knowledge" is that BP won't blow up your gun - ie it can't build pressure beyond around 15k or 20k cup depending upon who you talk to. I seem to recall, (but cannot find the source) that some late 19th centruy Europeans in the quest for large bore velocity, were reaching 40k ish cup or more but did not get the velocity desired.

The Lyman BP book shows a wide spread of pressures from ~ 13k to ~23k psi using the same load, same projectile. Substitue powders can increase pressure even more. Not surprising as they "burn hotter".

Burn rates were said to be constant.... until they weren't. variations in circumstances seem to cause odd anomalies.

Burn temperatures do not seem to be discussed.

And of course the closed vessel tests achieved pressures in excess of 100k "units said to be psi".... but that is yet another different scenario and discussion.


- chemistry
As The Mad Monk pointed out many times, the best charcoal produces the least fouling.

Other folks have added various things to try to make BP better. Plain sugar, iron oxide, fulminates, and potassium perchlorate amongst others.

The perchlorates are popular, since they provide both stabalization ( for which I am eternally greatlful!!!) and an increase in expansive gasses, thus more oomph. Unfortunately amongst the side effects are that they are harder to ignite in some firelocks; burn hotter and more agresssively; and deposit perchlorate salts. I am still researching what happens to the cyanides. These and the different "burn chemistry" can lead to different corrosion results.

Some additives seem to be stable, some not so much - witness your experience with unburned BlackMZ corroding your bore!

What has not been researched and discussed at length (to my knowledge - but I have been wrong before and expect to be wrong again) is the chemical processes that occur
upon ignition and combustion of these differrent compounds.

In some ways, this actually IS rocket science, since some of what we know of BP and much of what we know of sugar-based fuels comes from solid-propellant rocket reasearch dating back to Robert Goddard. That research however is more concerned with thrust, nozzle design, and "not exploding" and no one cares about corrosion since the engine nozzles are considered somewhat expendable.

I respect your education, applaud your open mindedness, appreciate your considered reply, and am interested in your tests!

I am continually amazed at how people have different experiences, but I am convinced by my many years in complex failure analysis that the variations in conditions are the key, thus the need for continuing conversations!

yhs
prof marvel
(please forgive misspellings & such, my brain is not getting along with my fingers so well as of late)
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Last edited by prof marvel; March 7, 2019 at 04:30 PM.
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