Scroll down about 1/4 for an explanation of Parker Bros. proof testing
https://docs.google.com/document/d/1...UOZEFU/preview
The 1893 Parker Bros Catalogue documented proof testing with Smokeless Powder in house
"Our guns are bored on the latest improved system for shooting Nitros, or Smokeless Powder, and all our guns are tested with some one of the most approved makes, and a tag accompanies each gun, giving the results of such a (pattern) test."
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.
"PARKER BROS. OVERLOAD PROVED" first appeared in 1925.
No ammo, of any pressure, should be used in a vintage gun, fluid steel or damascus, until after an evaluation by a specialist with the interest, equipment (bore scope and wall thickness gauge) and expertise to do so. If the barrels are free of defects and with adequate wall thickness (ignoring the recoil effect on the head of the stock) one should feel confident in using shells which reproduce the ballistics of those for which the gun was designed.
Threaded Mode