Jim:

You're having trouble finding pressure information elsewhere because little else is available.

As for the conversions that you asked about, it depends on what you're trying to convert, and the terminology in Wright's book is a little confusing. I won't say that it's wrong, just confusing.

Working from memory (to be honest, I found his book so useful that I gave my copy away), I think he refers to the original pressure standard for the Kynoch Cordite .470 load as 14 TPSI. That isn't really correct, because it's too easily confused with a measurement of something completely different. The original standard for the .470 was 14 tons BaseCUP (Base Copper Units of Pressure), which was a measurement of bolt thrust expressed in long tons at 2240 pounds to the ton. This value is a measurement of the force exerted on the breech face by the cartridge head as measured in a Base Copper Crusher pressure gun. This isn't chamber pressure, nor does it readily convert to chamber pressure. I seem to recall that some or all of the pressures for the handloads in his book were were also measured in base crusher guns at Kynoch and the Birmingham Proof House, which is probably why your conversions to chamber pressure with these figures seem off.

Chamber pressure is measured radially (on the chamber sidewall) via copper crusher (expressed as CUP, as opposed to BaseCUP) or piezo electric transducer (expressed as PSI or TPSI). The Norma pressure figure that you gave was converted to PSI, which is chamber pressure. The current CIP standard (max average) chamber pressure for the .470 is 2700 BAR or 39,160 PSI. So, yeah, Norma's load is within the pressure spec, but the velocity is too high.
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