This is my first go at creating a low / high poly model. 
14k Tris 
One 4k Map 
Reviewing this I would Change the small springs to a textured cylinder to further reduce my poly count. Also I would spend more time laying out my UV's.
Sten guns were produced in several basic marks (though the Mk I saw limited service, and the Mk IV was never issued), and nearly half of the total produced were Mark II versions. Approximately 4.5 million Stens were produced during the second world war.