Kent Tungsten Matrix 12 gauge 1400 FPS safe in a 3 frame parker?

[Cold Spring]

Originally Posted by Drew Hause

Western Cartridge Co. never marked the Super-X ‘Field’ or ‘Record’ boxes with “Dr. Eq.” stating only “Maximum Load”. It is presumed that 12g ‘Super-X Field’ 2 3/4” 1 1/4 oz. was 3 3/4 Drams Equiv. or 1330 fps, and the 3” 1 3/8 oz. ‘Record’ was 1275 - 1295 fps (the speed of 1 1/4 oz. 3 1/2 Dr. Eq. loads).

Thanks Drew for that additional information. Regarding the 3-inch 1-3/8 ounce load, I have a reference that its speed was 1315 fps, probably at 3 feet as generally measured in the US.

So now I have a question. Several of your posts here have referenced "Burrard's conversion" of tons (pressure) to psi. I've seen many period references in American sporting literature to shotgun breech pressure and stated in tons. For example, that production Winchester 21's were proofed at 7-1/2 tons. Another example from almost 90 years ago, verbatim, "pressure limit generally considered to be 5.00 tons per sq inch". The underscore is mine.

So, why would it be that American readers needed to reference a little known conversion to convert tons to psi as measured with lead crushers?

[Drew Hause]

Long version Frank

Wallace H. Coxe, in “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics” published by E.I. du Pont de Nemours & Co., 1927, “Measurement of Pressures”
The common method of taking pressures in small arms in this country is known as the Radial Pressure system. A housing is built around the barrel, and a hole drilled through the housing and barrel into the chamber at a distance of 1 inch from the breech and at right angles to the axis of the bore. The hole is then bushed and drilled to a uniform diameter of 0.2250 inch. Then a piston is made the length of the piston hole and 0.2250 inch in diameter. Next the piston hole is lapped to permit the piston to fit snugly without either sticking or getting out of alignment.
In firing the gauge, the piston is inserted and seated, then a lead crusher cylinder is placed on the head of the piston and held firmly in place by a screw and anvil attachment built into the housing. When the cartridge is fired, a portion of the same gas pressure that pushes the bullet through the barrel drives the piston against the lead cylinder and compresses it.
The length of the lead crusher cylinder after compression is naturally less than before the shot was fired and the difference between the original length and the length after compression therefore represents the amount of pressure which has acted upon the lead. Thee exact pressure is read from a table giving a pressure reading for every remaining length reading and commonly called a Tarage Table.
Pressures that are determined at ballistic laboratories are merely relative values and are not absolute values.

NOTE: The Tarage Table conversion may be for pressure expressed as Tons / Sq. Inch or Pounds/ Sq. Inch (PSI).

September 1931 American Rifleman. “Standard Shotgun Pressure Barrels”, by Merton A. Robinson, Ballistics Engineer, Winchester Repeating Arms Co. The article described in detail the crusher method of pressure testing, with images of pressure barrels then in use by Peters, Hercules, Western, Remington, Winchester, Du Pont and Federal. Although the barrels were of somewhat different designs, they were ALL crusher barrels, without evidence of piezoelectric transducers. (Courtesy of Larry Brown)

Major Sir Gerald Burrard published an estimated LUP (Long) Tons/ Sq. Inch (TSI) to piezoelectric transducer Pounds/ Sq. Inch (PSI) conversion formula in the Third edition of The Modern Shotgun, 1955, Vol. 2 derived from simultaneous crusher and transducer pressure readings in a test barrel. He observed 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…”

Estimated Long Tons Per Square Inch Lead Crusher Pressure (Cp) conversion to PSI (pound force per square inch) (Cp x 1.5) - .5 = TSI, TSI X 2240 = PSI. Using this formula:
3 Tons/sq. inch by LUP (crushers) = 8,938 PSI (pounds/ sq. inch) by transducer
3 1/4 Tons = 9,682 psi
3 1/2 Tons = 10,427 psi
3 3/4 Tons = 11,480 psi (The SAAMI maximum for 2 3/4” 12g is 11,500 psi)
4 Tons = 11,917 psi

“Eley Shooter's Diary 2005” - “The later transducer system uplifts the (PSI by LUP) values by approx. 14%.”

From the CIP site: confirmation that 850 BAR = 12,328 PSI by crushers (LUP) is actually 960 BAR = 13,924 PSI by transducers (13% higher)
http://www.chircuprodimpex.ro/produs...ammunition.pdf
“These cartridges, if they are to be fired from standard proof shotguns (ie those proved to 960 bar [transducer] or, previously, 850 bar [crusher]), or magnum proof shotguns (ie those proved to 1370 bar [transducer] or, previously, 1200 bar [crusher]) must not exceed the maximum admissible service pressure of 74 MPa (new units “megapascals”, in place of the old 740 bar) specified by the CIP and measured by means of a piezo-electric transducer.”



SHORT VERSION
If the tarage table conversion is expressed as psi - add 10-14% for modern piezoelectric transducer measurement
If the tarage table conversion is expressed as (long) tons - use Burrard's formula

[OH Osthaus]

it would be interesting to have some of those original revered loads tested to see how they actually perform in velocity and pressure

the loads (and some matching guns) were marketed to be game changers to the average shooter

i expect a great long range shooter like Nash Buckingham could make any satisfactory load look like a winner in Bo Whoop or any properly choked gun

[King Brown]

Kent TM 1 1/4 at 1500fps is too much generally for any American classic, in my opinion. I bought a Beretta 686 to handle it.

[Cold Spring]

Thank you Drew for all that work to explain the conversion. I greatly appreciate your efforts.

Just some thoughts: 1) that factor of 1.5 in the tons to psi conversion formula seems a little nebulous; and 2) all the period American literature I've seen uses the word "tons" as compared with "long tons"; and 3) I wonder why Burrard apparently didn't use the typical English "tonnes" to indicate the long/metric ton.

Some final comments, on the Kent TM velocity. I've tried but haven't been able to confirm where that figure is indicated. Whether that's at 3 feet, or is "extrapolated to muzzle velocity" as has been done on at least some UK shotshells in the past. That 3 feet makes a huge difference in speed (when measured so close to the muzzle) and of course a higher number sounds better in the adverts. Nonetheless I believe any Kent shotshell sold in the US adheres to SAAMI pressure standards, same as competing shells by US manufacturers. Maybe Kent has some secret magic gunpowder that produces much higher speeds than the US shell makers can do, but still at accepted max pressure?

[Drew Hause]

Coxe specifically stated in one of his DuPont pamphlets that the 'Tons' were 'Long Tons'

I still think the Brits just enjoy messing with us Colonials

[Kevin McCormack]

"Maximum, Maximum, Maximum".......uh, sorry; just got finished watching "Gladiator" for the 54th time before going online - Duh!

[Cold Spring]

Hello again Drew, further on that "Burrard's Conversion" of tons to psi:

I am still unconvinced it applies to converting tons to psi pressure as reported in American sporting literature. Just this morning I was reviewing tech info on Winchester 21's and I read Jack O'Connor (1949) who stated again that 21's were proofed at 7-1/2 long tons which he also cited as 16,500 psi. That's a simple multiplication without the little known "conversion" ..... 7.5 (2200) = 16,500

As I'm sure you know, lead crushers became outmoded after electronic pressure measurement came into general use in the US after the War.

All told I ask if you are sure that Burrard's conversion applies to American pressure as stated in long tons, or if it solely relates to British proofing? Thanks in advance for your reply.

[Cold Spring]

Deleted duplicate

[Drew Hause]

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



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.