6.5x54 MS is listed as CIP pezio at 53,000 PSI and 46,000 CIP copper units of pressure.

It would be absolutely impossible to achieve that speed with less pressure using today's powders I'm sure - when the slightly larger cases barely make it at yet higher pressure.

I made the mistake of assuming the long ton was the correct multiplier some time ago and was corrected by another site memeber here. This listing I just made is straight off this site below. I find it handy and the text also talks/explains the various methods and locations of measurement, between SAAMI and CIP.

http://kwk.us/pressures.html