Luger spring steel...

[sheepherder]

Originally Posted by John Sabato

You wouldn't need an outside "hole" for the adjustments as they would be seldom necessary once you achieved the appropriate tension. Initial adjustment would be made with the grips removed and a special spanner type wrench.

My thought was that the mainspring could be adjusted on-the-fly, to compensate for different loads/bullet weights. My experience with this has been the FN-49 which uses a gas regulator with different size orifices to increase or decrease gas pressure. I'm sure other rifles use a similar system [BrEN, FAL?].

If you didn't want to have a quick-access hole, then the nut could have flats (as you suggest) or holes for adjustment. That would require grip removal...

Interesting idea. If Rolf went to such pains to patent it, why did it never make it into production???

Either on the Mauser-Luger or as an accessory...