https://www.rockislandauction.com/detail/70/3447

The M-56 is a Yugoslav take on the MP-40 design, produced starting in 1956 to replace its previously issued M49 submachine gun (which was a copy of the Soviet PPSh-41). The M56 is simpler than the MP40, however, and chambered for the 7.62x25mm Tokarev cartridge. It is a simple gun to make, but quite awkward to use, and has a remarkable potential to disassemble itself while firing if not assembled correctly.

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