[mrerick]

The firing tests were intended to prove a number of things for the firearm.

Overpressure proof rounds confirmed that the receiver and barrel could tolerate high pressure without damage.

Also, the firearm cycled and operated properly.

Targets confirmed accuracy to an acceptable level at the designated range.

For safety, it's likely that a firing fixture of some type was used. I can't remember details, but I think that there are photos of the firing points of the test range in the Mauser archive.