I'm doing a little digging to try and nail down when the CIP countries dropped lead crushers for pressure measurement and converted to piezo-electronic transducers. So far, here's what I know:

Per the Birmingham Proofhouse, they were still using crushers as recently as November 2001. And as far as I know, the Brits continued to mark their guns (12 bores) 850 bars standard proof, 1200 bars superior, until they dropped all proofmarks with an actual pressure number in 2006. Those are crusher numbers.

The proof certificate of a Spanish double from 2001 shows a proof pressure of 1370 bars, which is a transducer number. So the Spanish Proofhouse had converted to transducers by then--but maybe not long before that. (I have a photo of a Spanish 20ga from 1999 which is stamped 1200 bars, which is the old, crusher-derived magnum/superior proof.)

I'd like to hear from those of you that either have guns with pressure figures included in the proofmarks, like Spanish guns or British guns from the "bars" era, if your gun also includes a date code. I'd particularly like to hear from those that have proof certificates on Italian guns, which are only marked with a symbol rather than an actual pressure figure. Specifically, I'm trying to determine when the Gardone Proofhouse switched from crushers to transducers, but I think it would also be of interest to determine when other CIP countries did the same thing. It would appear, from the evidence on British and Spanish proof, that they did not all make the conversion at the same time.

Finally, I'd note that the old crusher figures and the new transducer figures are simply different ways of expressing the same pressure. 1200 bars crusher = 1370 bars transducer, again per the Birmingham Proofhouse. However, if you're trying to convert your gun's proof pressure to psi, you can't multiply crusher values x 14.5. If you do, you end up with lead units of pressure (LUP), not psi. You can convert transducer-derived values, either bars or kilograms per square centimeter, by multiplying x 14.5.

Thanks in advance for your assistance!

Last edited by L. Brown; 01/10/14 08:51 AM.