Frank: the more we all think about this the better...and I still think the Brits enjoy(ed) messing with us :(

What I assume: The Tarage table used to convert compression of lead crushers (distance) to pressure reported either PSI OR Long Tons.

What I know:
This pressure/distance curve appears on p. 20 of "Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics" by Wallace H Coxe, 1931

http://pic20.picturetrail.com:80/VOL.../409804775.jpg

On p. 21 Coxe states "The vertical line represents the pressures developed by the various powders. This is measured in long tons (2240 pounds)."

Major Sir Gerald Burrard wrote in the Third edition of The Modern Shotgun, 1955, Vol. 2 that pressures derived from simultaneous crusher and piezoelectric transducer pressure readings in a test barrel demonstrated the under-reporting of pressure by (crusher) LUP compared to piezo transducer gauges:
“The calibration of lead crushers by means of the piezoelectric gauge suggests that lead crusher pressures are somewhat on the low side; 2 Tons per square inch being about 2.5 with the piezoelectric gauge…”
And for that reason he came up with his formula to convert pressure as measured by lead crushers expressed in Long Tons to PSI as measured by modern piezoelectric transducers.
That ALSO means PSI as measured by crushers is less than that as measured by transducers, and “Eley Shooter's Diary 2005” states “The later transducer system uplifts the (PSI by LUP) values by approx. 14%.” Other authors say 10% - 14%.

What we don't know:
When were pressures reported by U.S. gun and ammo makers measured by piezo transducers?

We DO know that the Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives standards ratified in 1969 expressed the pressure numbers as transducer BAR converted to PSI.

BUT the darn Brits didn't adopt the CIP standards until March 1, 1980.

Thanks again Drew, I agree that the more we study this topic, the better.

Your other assumption is, there was a standard "agreement" between the US makers and their British counterparts to use the same protocols for testing, to include a standard location for the crusher on the pressure gun, the same crusher diameter/length, and the same chemically pure lead or lead alloy whichever it was. Do we know if there was any such agreement? I've never read of anything like that in period literature and frankly I don't believe the Brits tried to coordinate their pressure testing apparatus and protocols with what the US makers were doing.

All told and thanks to your work, it seems that Burrard had a good handle on a conversion formula for pressures as measured by the British. Does Burrard specifically mention in his book that his formula applies to the US makers and their protocols when they measured tons or tons/sq inch with the old lead crusher technology?

Also who has any references to "Burrard's Conversion" in recognized US shotgun ballistic literature? I've seen many references where American makers reported pressure in "tons" and generally that's been accepted as: tons X 2200 (as I learned in grade school) or as tons X 2240 (as the accepted value is today). The difference between using the factors 2200 or 2240 is somewhat insignificant relative to this discussion.

I agree of course that old US lead crusher numbers should be multiplied by 1.10 to 1.15 to convert to transducer psi. Nowhere have I read or seen anything other than: tons X factor X 1.10 to 1.15 to convert to approximate psi.

I thank you again Drew for this effort and all the other study work you do. I hope to meet you some day. :)

It's been fun Frank, but hard for this non-engineer with a bit of math dyslexia - really a miracle I made it through chemistry and physics, but it was the U. of Mo. ;)

This is interesting

“Experiments by Mr. R.W.S. Griffith of the Schultze Powder Co.” in Sporting Guns and Gunpowder
https://books.google.com/books?id=in...AAJ&pg=PA38&dq

LOADS……….................……………..……………1 1/8oz….1oz.....7/8oz.
………………………………....................……………….12g…..16g…. .20g
Curtis & Harvey No. 4 T.S. Black Powder...….82….…74….…66 grains
Schultze and “E.C.” Bulk Smokeless.……....….42….…37….…33
Walsrode Dense Smokeless...………………........28…….24….…22
12g = 3 Dram or 3 Dr. Eq.
16g - 74 gr. BP = 2.7 Drams; 37 gr. Bulk = 2.64 Dr. Eq.; 24 gr. Dense Walsrode = 2.57 Dr. Eq.
20g - 66 gr. BP = 2.4 Drams; 33 gr. Bulk = 2.36 Dr. Eq.; 22 gr. Dense = 2.38 Dr. Eq.

Chamber pressures were expressed as Tons/sq. inch. If simply multiplied by 2240 the pressures are unreasonably low. Using Burrard’s conversion yields what seem to be accurate numbers:

………….....……..12……….16……...20
C.&H. No. 4…6,373…..7,078.…..6,944
C.&H. No. 2…7,459…..8,310...…8,288
Schultze……...4,424…..6,272.…..7,246
“E.C.”……..…..3,685…..6,171.…..8,322
Walsrode.…….9,363………......….10,741
S.S. …..….……9,800….....………….10,539
S.S. (Smokeless Shot-gun)

BTW: usually pretty nice in Vegas this time of year but rainy and cold Friday and yesterday with LOTS of snow across northern AZ. Come out to the show some time :)
Josh said he'd like to continue to have a significant Parker presence at the show.

Some additional data on American shotshell pressure measurement: Charles Askins reporting in 1929 on tests at DuPont's Brandywine Laboratory of the 12-gauge/3-inch load with a max charge of its Oval progressive burning powder, as "taken from a DuPont ballistic sheet":

37 grains Oval, 1-3/8 ounces of No. 6-shot ------> 4.50 tons per square inch

Now then, 4.50 X 2200 X 1.15 = 11,385 psi as converted to approx. modern transducer reading

Or, if you prefer, 4.50 X 2240 X 1.15 = 11,592 psi as converted

Right on par with the current SAAMI max mean pressure for 12-gauge/3-inch at 11,500 psi.

In net, I continue to believe that "Burrard's Conversion" doesn't apply to pressures of American factory shotshells and thus the guns designed for them.

i really like talking about the 3 frame parker 12 ga and the loads every body shoots..i have only shot 2 3/4shells with the 1 1/4 lead loads but i would not be scared to shoot heavier loads in it....my old 12 ga weighs 9 1/2 lbs so not much recoil it is a good squirl gun...charlie