Downloaded from Grabcad. Model uploaded by DOLUNAY TASARIM®.....however, he only uploaded it in a barely usable .sldasm file. I had to try several times with various programs to convert it into usable formats myself. The zip folder contains the original files as well as the following converted formats: .3mf, .obj, .stl, and .step.
original link: https://grabcad.com/library/sarsilmaz-1
M1337 Assembled Reference Model + Animated Model
Yugoslavian M56 SMG Reference CAD v1.0