Proofing Pistol for alcohol?

[bombdoc]

I heard about a type of pistol that would allow the strength of alcohol to be measured. Gunpowder was mixed with the alcohol and it was fired in a flintlock. The explosion would move a needle around a protractor and the higher the alcohol content the further the needle would move, and give a higher 'degree' of proof. I think I even saw a picture of one once, but I cannot find any reference to an example of this type of instrument anywhere on the Internet. Did this really exist, or did I imagine it?

I think you are getting things confused here..

The determination of "proof spirit" for tax purposes was set by the gunpowder test. 100% proof spirit when poured on gunpowder would just allow it to be ignited. It was a simple test for determining whether a sample of spirit was over or under proof.. there was no need for a device, you just made a pile of gunpowder, wetted it with the spirit and attempted to light it (preferably with a taper). If the powder ignited, the sample was over proof, if not it was under proof. In the days when many people carried gunpowder, it was a quick and easy test to perform to check if spirits had been watered down!

Gunpowder testers or "Eprovettes" were used for testing the strength of gunpowder either for assessing quality of manufacture or to detect deterioration in storage. They were not that accurate, but gave a useful empirical comparison in the days when testing technology was less scientifically grounded. Government agencies tended to rely more on a calibrated mortar for proof testing. A small sample of powder was used to fire a standard ball at a fixed angle of projection. The ball had to reach a certain distance for the powder to pass acceptance proof (typically 100 yards or so).

Beware of buying antique eprovettes - there are a lot of fakes out there as in many countries these do not fall under firearms rules..