Belgian Percussion Eprouvette

This contraption is a Belgian Percussion Eprouvette. Back in the days when blackpowder was of dubious quality, devices like these were used to test the potency of the powder at hand. The barrel plug is attached to a V shaped spring. When fired the spring compresses moving a slider. The strength can then be read off a scale. I am not if the units on the scale correspond to the energy of the powder, or if it is just used for comparative purposes.

This particular Percussion Eprouvette is housed in the National Firearms Museum’s Robert E. Petersen gallery.

[ Many thanks to Nic Jenzen-Jones for emailing us the link. ]

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Doug

    Very cool. I wonder what that’s worth.

    Perhaps I’m misunderstanding the mechanics, but shouldn’t the larger numbers be farther away from the muzzle?

    • AD

      It looks to me like the top bar (with the scale) is actually pushed away from the muzzle, so the slider will be pushed along it (from smaller numbers to larger) by the far side of the spring.

    • gunslinger

      it looks like the side closest to the barrel is the part that moves. but right on the other side, it looks like there’s a loop for some type of lock or something. wouldn’t this get in the way when that section moves?

      • mouldysquid

        In the close up, it looks to me like the scale is split or “hollow” allowing a plug on the end of the spring (which is inside the hollow) to move. The ring is probably there to keep the frame from moving should the weld not hold.

  • Fred Johnson

    Very interesting device indeed. Thanks for the post.

  • Daniel

    I love how they engraved even a piece of test equipment. It’s a shame to see that level of craftsmanship absent from today’s products.

    • alannon

      I would say artisanship rather than craftsmanship. Our toys are built to a degree of precision (and therefore interchangeability and reliability) that they would have happily traded their engraving to achieve. 😉

      Also, when you look at equivalently-priced equipment (guns being affordable by us peons is pretty new), it’s still prettily engraved. When you stopped seeing that kind of work on every firearm is when they started becoming something average people had in their closet.

  • Kurt

    Cool. I learned a new word today.

  • Unistat

    That is pretty flipping awesome. It appeals to both the gun-dork and the history-nerd in me.

  • Isaac

    Whatever you do, don’t stick your finger between the forks during firing……

  • glenn b

    Nice piece, interesting. I would love to see one at the next gun auction I attend. I would definitely place a quick bid or to. Probably would not have the high bid but stranger things have happened at auctions.