Circa 1900-05 Live Bird gun

[Drew Hause]

Thanks Frank and I can't reconcile those numbers with Coxe's pressure curves or the 1927 SuperX flyer; 1000 fps at 40 yards, with a breech pressure of 3 3/4 tons or about 11,480 psi by Burrard’s conversion.
Coxe was the Ballistic Engineer at Brandywine

[Cold Spring]

And Drew thank you too.

I have been and still am very dubious that Burrard's conversion has any meaningful application to period American shotgun lead crusher pressure numbers.

Consider this on the DuPont Lab data cited by Askins and shown in my cell phone inset:

4.70 tons/sq inch X 2240 long ton pounds X 1.10 rough conversion from lead crusher tons to transducer psi = ~ 11,580 psi which is on par with industry standard average max pressure for 2-3/4" 12-gauge.

[Drew Hause]

And to confuse thing further

1933 lawsuit against Remington Arms related to the burst barrel of a Baltimore Arms Co. shotgun after using a Nitro Club marked Proof Load.
https://books.google.com/books?id=7p...C&pg=PA120&lpg
https://books.google.com/books?id=7p...C&pg=PA127&lpg
The “maximum commercial load” was described at “11,200 psi and 5 long tons” = 15,680 psi by Burrard’s conversion.
The proof load was “7 1/2 long tons or 17,800 psi”; 7.5 tons is 24,080 psi by Burrard’s conversion.
The simple formula conversion for 7.5 long tons is 16,800 pounds, which we understand doesn't work for LUP to PSI, but I wonder if the 7 1/2 to psi was miscalculated?

A Parker Service and Proof Load table was published in the 1930s and reproduced in the The Parker Story p. 515. 12g 2 3/4” shell Service Pressure is 10,500 psi. Definitive proof used 7.53 Drams Black Powder and 2 oz. shot with a pressure of 15,900 psi. The pressure was no doubt measured using LUP and modern transducer values would be 10-14% higher, or more than 17,500 psi.

LTC Calvin Goddard reported the same numbers in “Army Ordnance”, 1934. He wrote that Parker followed the SAAMI standards of that period: 13,700 psi proof, 9500 psi service for 2 5/8” chamber; 15,900 psi proof, 10,500 psi service for 2 3/4” chamber (by LUP) + 10-14% for modern transducer measurement.

[Drew Hause]

Here's the 1927 flyer; by Askins



3 1/2 Dram Bulk Powder = "3 3/4 tons" = 11,480 psi by Burrard's conversion



No clue as to how 3 1/2 Dr. Eq. Bulk became 4.7 tons/sq. inch in 1933

[charlie cleveland]

love reading these comments by atkins and others...charlie

[Cold Spring]

I'm familiar with that Super-X brochure and have a few of them with different color covers. As I read the text, the breech pressure of the Super-X progressive powder load is 3-3/4 tons. Also reading, that progressive load is safe in guns made for the old 3-1/2 dram load of bulk powder - but no pressure is cited for that old load in the text shown here. It's likely that old 3-1/2 dram Bulk load is similar to the one I referenced earlier that gave 4.70 tons/sq inch with 1-1/4 ounce of shot according to DuPont's Ballistics Lab.

(COPIED) 4.70 tons/sq inch X 2240 long ton pounds X 1.10 rough conversion from lead crusher tons to transducer psi = ~ 11,580 psi which is on par with industry standard average max pressure for 2-3/4" 12-gauge.

Burrard's conversion was not used in the snippet I copied.

Askins also wrote that progressive powder loads would generally produce higher velocity at standard service pressure, or (with a reduced powder charge) regular velocity with lower pressure. That was due to what he called the "barrel burning time" of progressive powders which in one test of DuPont's Oval was nearly twice as long as that of the dense powder to which it was compared. It should also be noted that several of Dupont's progressive burning powders were utilized by Western in its earliest Super-X shells before the company switched to its own powders, and one of DuPont's in particular was remarkable in producing high velocity with relatively low pressure but it was very expensive to produce.

Again, I am very doubtful that Burrard's conversion has any real application to period American shotshell lead crusher pressures as expressed in tons/sq inch. On that line I strongly suggest that Drew (who I respect greatly for his work with composite barrels) include a note on future postings that his use of Burrard's calculation may not be universally accepted. Thank you Drew for your consideration.

frank

[Drew Hause]

Double post

[Drew Hause]

These are the earliest pressure numbers I've found reported as psi (measured by LUP) rather than tons

1892. Service charge 1 1/4 oz. 3 1/4 Dr. Eq.
https://books.google.com/books?id=in...AJ&pg=PA296&dq




The Overland Monthly, Oct. 1895 “Smokeless Powder For Shotguns” with higher numbers
http://books.google.com/books?id=Wv0...J&pg=PA446&lpg
p. 453
3 1/4 Dram Eq./40 grains DuPont Bulk Smokeless 1 1/8 oz. (1255 fps) = 7440 psi
3 1/4 Dram Eq./44 grains “E.C.” Bulk Smokeless 1 1/8 oz. = 7584 psi


For comparison, a DuPont loading manual from the 1960s listed DuPont Bulk:
3 1/2 Dr. Eq. with 1 1/8 oz. shot at 10,000 psi
3 1/5 (3.20) Dr. Eq. with 1 1/4 oz. shot at 9,900 psi
(Probably measured by LUP)

[Drew Hause]

From the 1928 edition of “Smokeless Shotgun Powders” by Wallace Coxe
"DuPont Oval can be loaded with 1 3/8 ounces of shot in a 12-gauge shotgun to develop the same velocity and pressure as obtained with a load of 3 1/2 drams of DuPont Bulk Smokeless Powder or 28 grains of Ballistite and 1 1/4 ounces of shot."

Coxe reported 3 1/2 Dram Eq. 1 1/4 oz. load (1275 fps) pressures, measured by crushers (LUP) and expressed as psi:
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite Dense smokeless powder - 12,600 psi
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi

I think these are the best period numbers available, recognizing that modern piezo numbers would be 10-14% higher.

If we divide 11,700 by 2240 we get 5.2 tons which would fit the 1933 lawsuit numbers:
The “maximum commercial load” was described at “11,200 psi (divided by 2240) = 5 long tons”.

“Highest Mean Service Pressure” equivalent PSI transducer values as converted from LUP by Burrard’s formula (Cp x 1.5) - .5 = TSI, TSI X 2240 = PSI:
2 tons/sq. inch (NOT 2 X 2240) = 5,600 psi (pounds/sq. inch) = 386 BAR
2 1/2 tons = 7,280 psi = 502 BAR
3 tons = 8,960 psi = 618 BAR
3 1/4 tons = 9,800 psi = 676 BAR
3 1/2 tons = 10,640 psi = 734 BAR
3 3/4 tons = 11,480 psi = 792 BAR
4 tons = 12,320 psi = 850 BAR

Tons to psi by piezo transducers conversion provided by the Birmingham Proof House 11-2001 (courtesy of Larry Brown) are very close to Burrard's
2 1/2” / 3 tons = 8,938 psi
2 3/4” / 3 1/4 tons = 9,682 psi
3” / 3 1/2 tons = 10,427 psi
3” / 4 tons = 11,917 psi

I think Coxe was simply doing a formula conversion long tons/sq. inch to PSI using 2240. They were not using piezo transducers to measure psi in the 30s.

[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