Originally Posted by graybeardtmm3
Originally Posted by Drew Hause
Ted, Gene and FAB are the French experts. This is a long thread regarding French powders and proof
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=618070

The double preliminary proof indicates the tubes were proved at 16,356 psi + 10 - 14% for modern transducer measurement
The single Crowned PT indicated final proof at 12,090 psi + 10 - 14% for a service pressure of about 9000 psi

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I can't make a 'GAF' out of the Fs listed here
https://www.littlegun.be/arme%20belge/a%20a%20artisans%20identifies%20gb.htm#F
and, a "point of order" regarding the use of the term "double proof" - and this gets pretty sticky. using steindler's translation of wirnsberger's text on proof marks....from some point (could be 14 july, 1860; could be 22 april, 1868; could be 1869) st. etienne offered a standard "single proof" (consisting of a single st etienne mark), or a "re-enforced proof" (shown by two marks). at no point in his text is the term "re-enforced proof" presented as a double proof, there are three different places where he states "the double imprint of these marks signified re-enforced proof".

then in 1885, the parliament approved new rules, which were signed into effect by the president - and this is the event that (inadvertently) canceled obligatory proof in france. and until france joined the rest of the proof countries (at the international proof conference in 1914), all proof testing in france was purely voluntary. steindler states that the arms makers never ceased to proof, and that "the french arms industry gained rather than lost ground and prestige". during this period the marks themselves remained (largely) unchanged.

in november 1895, the paris proofhouse was established, and accepted the st. etienne rules for semi-smokeless proofs. as of 30 july 1897, double marks still indicate re-enforced proof, and at some point in 1901, a more powerful proof was introduced in st. etienne (and quickly adopted in paris) - and this where it gets sticky - THREE marks indicated double proof, and FOUR marks indicated triple proof.

"On the 18th December 1923, new proof rules were introduced. Retained was the standard and re-enforced proof which was not identical to either the double or triple proof mentioned above, but the proof marks remained the same. Consequently, it has become almost impossible to attempt to 'date' a gun by means of the proof marks unless the year of proof is known. While high or excessive pressures may well show up a fault, either in material or design of a gun, the exploitation of high pressures as a means of advertising became wide spread in France."

then on 4 june, 1926, to conform with international standards, french proof marks became typical (and much more easily understood)....one mark is standard (14,223 psi), two marks are double (16.356 psi), and three marks are triple proofed (18,490 psi). if you reference the chart that docdrew provides you will see that it pertains to this post 1923 era....and that fact leaves a large number of guns marked with powder T (starting around 1900) and coming forward until 1923-4, that are subject to much conjecture if they are marked with either two or three stamps. based on my understanding, a single stamp will always mean the same thing - and four stamps will always mean a triple proof (sometime between 1901 and 1924). but, two or three stamps are easily misinterpreted....this should give everyone a chance to scratch their head!

best regards,

tom

wanted to revisit this thread discussing french proofing of shotguns, and add to what i had to say regarding the confusion with two proof marks - as to whether they had been double proofed, or superior/re-enforced proofed.

there is a mf robust gun currently at auction on gunbroker that has some potentially useful markings....https://www.gunbroker.com/item/1065265989

the tubes have two proof marks - and are accompanied by "epreuve officielle superibuhe" (?), which clearly indicates that the proofing was the re-enforced proof....additionally the gun has chamber markings in cm's. from a posting by argo44 on 10 sept 17 (post #489750) there is a listing of model numbers used on robusts - which indicates that model #8 was introduced in 1914, and last shown in 1922....a production period of nine years, which may provide some additional measurement on both those uncertainties.

and, i also am caretaker of mf ideal #26831, which is listed as a 1906 gun, that has three proof stamps, and is also marked "double epreuve", and has chambers marked in cm's - "7". this gun is a "directors marked" special order gun.

so, nothing that settles things for-once-and-for-all; but a bit more information....at least mf marked some guns (upper grades?) with definitive evidence of what the number of stamps actually meant.

best regards,

tom


"it's a poor sort of memory that only works backwards."
lewis carroll, Alice in Wonderland