This is out of the Parker Story, Volume 2, page 515 and is for 12 gauge 2-5/8" chambers. TPC states that the article states that Parker adheres to the standards in the table.
Nominal Chamber and shell length - 2-5/8"
Theroetical Service Pressure limits Based on Definitive Proof Pressures
Mean: 9800
Maximum Individiual 12,000
Service Working Limits for Factory Loaded Ammunition
Mean: 9500
Maximum Individual 10,800
Notes on the table say that the units I gave are pounds which I take to mean psi
The table was in a 1934 article
One of the notes in the table said that the limits are based on 1925 British Rules and Regulations
I surmise that the psi and ton pressure measurement are in LUP which I think stands for "lead units of pressure." One of Burrard's volumes has a conversion for LUP to electronic pressure measured units. I have never been able to confirm that the table this is taken from is in LUP.
I shoot Federal Top Gun 2-3/4 dram 1-1/8oz loads in my Parker VH 98XXX, 7-1/2s and 8s. This gun is 2 frame with 30" barrels and weighs 7lbs 13 ounces. It had the chambers lengthened to 2-3/4" before I got it. I have measured the chamber wall thicknesses at the end of the chamber and the thinnest is .110". I use the gun for clays and for field trialing.
My gun was made well before 1934.
You pays your money and you takes your chances.
Best,
Mike
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