I was wondering if anyone had a standard copper units to pounds per square inch conversion value that they would post. I was looking at some of the Hodgdon 45 colt data listed in CUP but I only know the operating capacity of a Ruger Blackhawk in PSI.

Thanks for your help,

-Catter

Wildcatter,
It cannot be done reliably across the board. In some cartridges, CUP is approximately equal to PSI in magnitude (Like the 45/70 cartridge?). For most cartridges, the CUP numbers are lesser magnitude. For example, IIRC, for the 416 Remington Magnum, max pressure allowable by SAMI governing body is 54,000 CUP or 64,000 PSI.

The conversion factor differs from cartridge to cartridge and would only be an estimated value for a given cartridge where the governing body specifies a max pressure allowable and lists the pressures by both methods. And the Euro's did their CUP's differently from the Americano's. They are not equivalent. Peizo PSI 's would be more universal.

The CUP is kind of contrived. I like PSI better. I say they ought to convert all pressures to PSI, but then there is all that old pressure data that would have to be tested again instead of just passed down from the old days.

Does anyone know if the governing body lists a max allowable pressure for the .44 RM mag? It might be 39,000 CUP = 39,000 PSI. I would have to go to references to see.

There is no direct conversion factor.

For examples of PSI and CUP pressures I have them listed at:

http://stevespages.com/crusher.html

SAAMI has maximum pressures for all of the factory loaded american cartridges, and occasionally has a regulated +P pressure level (as in 38 Special) also. The real difference between factory and wildcat cartridges is the factory cartridge has a SAAMI specification, and wildcat cartridges don't. Europe uses an orginazation called CIP, which SAAMI consults with for cartridges that originated in europe but are loaded in the U.S.

I think the 44 Magnum is down to 36,000 psi, but I haven't yet bought the SAAMI manuals to know for certain.

SAAMI web page

Hint - the instructions for ordering the manuals are under the "Community/PR" tab, not the "Technical" and not the "Publications" tabs where you will probably look first.