Hi,
I doubt it. It's difficult to interpret the writing fully, but it just appears to be some regular 'chit chat' which is normally found on a post card someone sends home.
Probeschiessen can be translated as 'testshooting' or 'target practice', something the officers on the front of the card appear to be doing. The 'shooting investigation' translation on the page is a bitt off
The 1917 LP08 manual is also available as a reprint by Journal-Verlag Schwend GmbH, 74532 Schwabisch Hall, Germany. I bough one, together with a P08 manual reprint and a K98 manual reprint a while ago.