Any Internal Ballisticians Here?


#1

I would be very interested in finding data regarding the comparative differences in chamber pressure-time (or barrel position) curves (Piezo method, not LUP or CUP) of black powder and equivalent factory smokeless powder loads for any of the old black powder era revolver rounds such as .38 S&W, .44-40, .45 Colt, etc. After searching the internet, I haven’t found any worthwhile information, but I feel that it should exist somewhere. The Lyman black powder handbook contains a little information on LUP determinations for different charges of BP in cap & ball revolvers, but it’s of minimal value.


#2

Dennis
I suspect the information already exists, the hard part is locating a source and obtaining a copy.
I’d suggest contacting some/all of the following: White Labs (yes, the one founded by H.P. White, they do independent testing), Nosler Bullets, Sierra Bullets, Hornady Bullets, Hodgdon Powder, etc.
You may not get a full data set from any one source, but they each should be able to provide a piece of the puzzle. Their biggest concern will be potential liability exposure, so be prepared to ease their worries.
Worst case (and the best chance of getting exactly what your after) would be to instrument (strain gauge) a barrel and run your own tests. A local engineering school might be willing to take on the project, as part of a students “capstone project”. I assisted a friend on his capstone, where he was testing the effects of ammo temp on pressure and velocity. The instructor mounted the strain gauges, and a recent grad loaned them (the Friday night to Monday morning kind) a $20+k data acquisition package to collect the numbers. Rifles are easiest to deal with, due to the longer curve. Next would be a single shot pistol (Contender type). Both of these eliminate the “barrel gap” and “over chamber” problems found in revolvers.


#3

Try here :

R.S.I . Pressure Trace
shootingsoftware.com/pressure.htm

I have the older version and have not used it yet.

Glenn


#4

I also have an RSI system and have used it for about 12 different cartridges. mostly all rifle. Limited shotgun testing. Several were wildcats of my design. Some testing was done with a H&H double rifle that I have owned for some time that is chambered for 450-400 2 3/8" BP. I was successful in creating nitro for BP loads that regulated and were at safe pressure levels. That was the only BP cartridge. The strain gage system is relatively inexpensive and does no damage to the finish of the firearm. However. I do not believe it will work with a revolver as the cylinder does not have uniform thickness and I do not recall the software having parameters for use with revolvers. I believe a test barrel with uniform wall thickness would be necessary to calibrate to provide accurate readings.
Attaching a strain gage to a revolver cylinder in this system is not at all practical. RSI’s web site, while not the most user friendly has a lot of info if you poke around. Some of the tech articles are quite informative.


#5

I have actually used both piezo gauge and strain gauge methods for determining chamber pressures, but the equipment was not mine. The strain gauge system works quite well. The ideal setup, and reasonably affordable, for testing pistol caliber ammunition would be to use the strain gauge method combined with a T/C Contender barrel(s) chambered in the appropriate caliber(s). I don’t believe attaching a strain gauge to a revolver cylinder would work very well. I do not know how well the strain gauge method would work for lower pressure pistol cartridges.

However, I’m not interested in pursuing a research project to answer to my original question to the extent that I would make such an investment or employ any extraordinary measures. I was merely inquiring if anyone had such comparative pressure data available, as I had never seen any information of that nature (i.e., black powder vs smokeless chamber pressure curves for comparable muzzle velocities). If not, no big deal.


#6

It would be interesting to do but way beyond my capability Black powder cartridges of the type you list would be so slow to build to pressure compared to smokeless. I would love to see your results. it would be an education.


#7

That’s exactly what I want to know - rise time and peak chamber pressure of BP vs. smokeless in loads of equivalent lead bullet weight and velocity. I have diligently searched for such data on the internet, but without success, nor do I recall ever reading anything about it. It would necessarily have to be obtained by either a piezo or strain gauge, as LUP (or CUP) methods tell virtually nothing about the instantaneous peak pressure or the shape of the pressure curve. The conventional wisdom suggests that smokeless would produce a higher and shorter peak than an equivalent BP load, but I’d like some quantitative evidence.