[Shondi]

What do these letters "cup" mean at the end of the pressure statement in the reloading manuals. Thanks.

[SDC]

It stands for "copper units of pressure", an old method of measuring pressure when a gun was fired. They used what was called a "copper crusher" fixture, where a barrel with a hole in the chamber was installed in a vise, a copper slug was put into that hole, a cartridge was chambered and fired, and the amount that the copper slug was compressed would let them know how much pressure that load had produced. (They did the same sort of thing with a lead slug for lower-pressure shotgun loads, so you sometimes see shotgun pressures expressed in "lead units of pressure", or "lup"s). Both of these are essentially obsolete now, since they use piezo-electric strain gauges that give more accurate measurements over the entire pressure wave, and not just the single highest point.

[USSR]

Good, easy to read explanation, SDC.

Don

[Shondi]

Thanks SDC for the info.

[jim147]

I remember when Olathe was in the country and Gardner was the sticks. Now you have to go way past there.
SDC gave you some good info. If you want more you can google copper units of pressure and you might check out lup also.

jim

[ReloaderFred]

There was an excellent article by Allan Jones on this subject in the May, 2009 issue of Shooting Times Magazine. He explains why Speer went to the Piezo-electric testing method with Speer Reloading Manual #12, and why they changed some of the data.

Hope this helps.

Fred

[SSN Vet]

and to wind it up...

there is no 'conversion factor" to go from CUPs to PSI...

and if anyone tells you that their is one and they no what it is... beware!

It's kind of like Rockwell Hardness.... the exact data points are inextactable from the the specific test equipment set up. Given the ready availability of the test equipment and it's wide acceptance, the daya is extremely valuable for compaiing the hardness properties of different sample.