My friend Tim loaned me his Kreighoff gage so I could make a gage for myself.
Thought all would like to see the gage.
Firing pin protrusion from the bolt face specs are between 1.1mm(min) and 1.35mm(max).
The 1.1mm side of the gage is placed against the breech block to the side of the firing pin, the pin must not pass under the cut out; if it does it is too short.
Flip the gage around, and the 1.35mm side should pass over the firing pin, if it does not - it is too long.
A long pin tip can be stoned to shorten it, the tip should also be nicely rounded, not "pointy".
Also shown is one of the gages I made in similar pattern; I chose to "straw" mine.