Luger spring steel...

[sheepherder]

Originally Posted by Vlim

An interesting side note is that Rolf took out a patent on a design for an adjustable main spring for the Mauser Parabellum. The solution was actually quite clever. The bottom of the spring hook was constructed with a threaded bushing, where a set screw could be screwed in. By adjusting this set screw, the spring tension was increased or decreased.

I'm not sure that it was a 'setscrew' (although I haven't tried to read the text)...

Looking at the second drawing [below], it looks like a split nut, with the nut being spirally split...

From the pics, I can't figure out how Rolf adjusted it...

I had envisioned a long nut with a simple slot [for a screwdriver] and a threaded mainspring guide...You'd need outside access as well [a hole]...This actually sounds do-able...