Circa 1900-05 Live Bird gun

[Cold Spring]

This will be my last post on the subject. I'll bet a lot of readers are baffled by all the numbers shown in many posts on this thread.

An analogy that comes to mind here would be: for someone to take automobile engine horsepower ratings from the 1920-30's or so, and try to compare with modern engine horsepower ratings. Yep horsepower is horsepower. But that person has no idea if the dynamometers (if any) used back then were all calibrated from auto maker to auto maker and if the results obtained with that relatively primitive equipment and converted from torque to horsepower are all dead nuts accurate - as compared with current horsepower ratings made using modern technology.

Why does this analogy at least partially fit? Because many of us are using vintage SxS shotguns and are relying on period lead crusher ton or even period psi pressure numbers to cipher what we can shoot in them relative to modern transducer psi ratings. But when using those period pressures no allowance is being made for the relatively simple gunpowder manufacturing technology back then and even small differences in % of nitrogen (money number) in various lots of the powders, addition/deletion of powder additives, and advances in shotshells such as roll crimps morphing to star crimps, different wadding materials over the years. etc. On that line it's no different than looking at a modern shotshell loading manual for a specific powder charge weight and hull, and seeing the differences in pressures by substitution of alternate primers and wads.

Sorry for my rambling here, but I come back again that a good approximation of vintage lead crusher numbers to modern psi, may be made by taking the tons/sq inch X 2240 X 1.10. This will yield a number that hasn't been enhanced by the addition of yet another conversion factor that, in sum, might make gents think that certain vintage shotguns and barrel materials were designed for higher pressures than they may have been.

FINIS

frank

[Double Lab]

No apologies necessary Frank. I think most of us here, especially those of us that reload, pay attention to this type of data. We may not all comprehend the technical aspects of these formulas but I for one find it interesting and useful and your analogy to horsepower ratings was quite appropriate.

Thanks also to Drew for the reams of info he distributes over this forum.

[Drew Hause]

As a victim of a public education in the great State of Missouri K - post-graduate I'm not so good with numbers. I think we are all just trying to understand, despite we and the British speaking a different language

A not unreasonable summary, which Bro. Bruce has been telling us for years, is that there is no reason to believe turn-of-the-century Bulk (and esp. Dense) Smokeless Shotshell pressures were much different than today's loads.

The fluid steel and pattern welded barrels were not 4140 however, many are now 100 years old, and some were neglected or abused. I think we also understand our margin for error is less.

[Drew Hause]

It does appear that Coxe was simply converting tons X 2240 to derive psi.

From “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics”, 1927, a DuPont Oval Pamphlet, p.20.
Dram Eq. is listed on the graph as 3; charge was 1 1/4 oz. Pressure is expressed in Long Tons.

Using Burrard’s estimated Tons Lead Crusher Pressure (Cp) conversion to PSI (pound force per square inch): (Cp x 1.5) - .5 = TSI; TSI X 2240 = PSI in BLACK
IF Coxe was simply converting Tons X 2240 to estimate the PSI in BLUE and is compatible with other 3 Dr. Eq. published measurements (+ 10-14% for modern transducer numbers)

Ballistite maximum pressure at 1” was 4.9 Long Tons = 15,344 psi (by Burrard) or 10,976 psi
Schultze at 1 3/4” was 4.5 Long Tons = 14,000 psi or 10,080
DuPont Bulk at 1 2/3” was 4.1 Long Tons = 12,656 psi or 9,184
FFFg at 1 1/2” was 3.8 Long Tons = 11,648 psi or 8,512
DuPont Oval at 2” was 3.5 Long Tons = 10,640 psi or 7,840

I wish he'd just used the Tarage table for psi instead
Or maybe he did, and for some unfortunate reason chose to express the numbers as Long Tons??

The BLUE psi numbers are similar to “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics”, 1933. The pressure curves (PSI by LUP) are also for a 3 Dr. Eq. 1 1/4 oz. load (+ 10-14%)
DuPont MX = 9,800 psi
DuPont Bulk = 9,600 psi
FFFg = 9,000 psi
DuPont Oval = 8,700 psi