Eprouvette

An eprouvette is a one piece, fixed elevation mortar used by ordnance departments and armories to test the strength of gunpowder.

A carefully weighed quantity of powder (charge) was placed inside the device, followed by a standard weight shot.

The charge was fired and the distance the shot flew was measured and compared to the expected standard distance.

[1] Eprouvettes were also used to test the strength of small-arms powder, starting in the second half of the 1500s.

These evolved into pistol-size devices which were used until the end of the black powder era, at the close of the 1800s.