# Proof formula

jimrbto

August 21, 2008, 10:09 PM

While going through my safe today I came across the original proof of proof card that came with an 1851 Navy Colt I bought in Germany back in '59, try as I might I cannot find this formula anywhere except for a concrete peneteration meter. As stated on the card the gun was proofed at "620 Kgr/cmq". I have seen a lot of formulas in my day but never this one. The "cmq" is the part I have never seen before.

Any ideas?

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Drgong

August 21, 2008, 10:23 PM

sure it not Cm2?

In that case it was proofed to 8,800 PSI or so...

Omnivore

August 21, 2008, 10:46 PM

Pressure per unit area. Square centimeters would definitely make sense, as the units would be consistent. Sure it's not "cmsq"?

jimrbto

August 22, 2008, 12:14 AM

I should have said that this "shoe tag" is all in Italian. The front is preprinted with spaces to write in the serial no. etc. If needed I can type everything that is on the card and on the back but the part I am interested in is on the front and states:

Pressione di Prova Superata

620 Kgr. / cmq

I am assuming that the above is the proof data.

Perhaps back then the Italians had a way or stating a formula we aren't familiar with?

Thanks .........Jim

mykeal

August 22, 2008, 12:26 AM

Centimeters squared in Italian is "centimetro quadrado", abbreviated as cmq.

bigbadgun

August 22, 2008, 08:45 AM

Pressione di Prova Superata=Pressure to Pass Test

Best I can offer

Drgong

August 22, 2008, 10:43 AM

Your gun was proofed to around 8,800 PSI, as it is the Kgr/cmq is multipied at 14.xx (I think it is 14.22, but I can be wrong) to get PSI, which gives you the PSI of around 8,800 PSI.

jimrbto

August 22, 2008, 03:35 PM

Thanks everyone, I assumed that the "cmq" probably meant sq. cm.

however you all know what ass-u-me means. When I googled that formula and came up with four hits all pertaining to concrete penetration it kind of threw me.

That means that my barrel was proofed to 8818 lbs/sq in. I wonder what the proof standards are today for bp barrels of various types.

Thanks again

Jim

Jim K

August 23, 2008, 01:38 AM

That is, of course, the black powder proof, as the "PN" (polvere nera) proof mark shows. Smokeless powder proof pressures for modern guns would be much higher.

I am sure the proof loads are the same today, and would be the same in every country that has a proof law. Once set, those proof rules rarely if ever change unless there is a new type of powder (as in the change from black to smokeless around 1900).

Jim

Loomis

August 23, 2008, 02:25 AM

Pressione di Prova Superata

Proven beyond pressure

Prooven to exceed

minimum proofed pressure

you get the idea.

mtngunr

August 23, 2008, 02:53 AM

And it means the cylinder, not barrel, held proof....getting over 8000psi in a front-stuffer cylinder was plenty....

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