Mauser Selbstlader

The Mauser Selbstlader (“Mauser Self-loader”) was one of the rifles issued for use in aircraft early in World War I. The design gave very accurate fire, but at the price being intolerant of dirt or grime. It required lubricated cartridges for extraction, and has very tight manufacturing clearances, which were a show-stopper for ground troops but not a problem for aviators.
If you wish to see disassembly instructions for this family of rifles, as well as good photos of all the internal parts, you can take a look at the manual on the link here.