It was an SS experiment that went nowhere. The SS wanted an alternative to the MP40 which gave problems at the eastern front.

But since running changes to the MP40 were already planned and the MP SS 42 would use the same magazines, a source of many issues, there was not a lot of need to replace the MP40.

Main requirements of the SS were:
9x19 cartridge use.
Single shot and auto fire modes.
A wooden stock to prevent the stock from freezing to the soldier's face.
Improved safety feature for cocked and uncocked state.

During a meeting on the 28th of August, 1942, the SS was advised to rethink the idea and await the planned StG.