Just had a look at Fowler's Modern English Usage: it's not very helpful.
OED states "prove" can be to "subject to a testing process"; proof can be "6. The action or an act of testing something"; or, better still: "9a The testing of cannon or small firearms by firing a heavy charge or by hydraulic pressure" and "b a place for testing firearms or explosives".

So clearly we have proof houses, which prove the fitness of small and other arms in a process called proof (is the act of that proofing or proving?), but I can still not say whether an arm so proved/proofed/proven is, properly speaking, proofed, proved or proven!

I'm inclined to believe, though, that properly, a firearm is more likely to be proofed than proven or proved, and that a proof master is likely to be proofing a firearm before he is proving it given the specific technical sense of the word.
You may be right, GregSY, that if a condemned man is "hanged by the neck until dead", but his clothes are hung out to dry, that most things can be proved or proven, but guns are proofed...
RG

Last edited by cadet; 07/31/09 12:00 AM.