This is what I have observed about the Mauser "hump". There are no measurements other than by eyeball and magnifier here, and I have not done any practical experiments, but this may be a useful path of inquiry:
The thickened back of the early Mauser frame changes the geometry of the workings of the toggle. The toggle stop meets the frame back a mm or so sooner than the original guns, thus the toggle does not open quite so far and the breechblock does not go quite as far back.
You will observe that the "hump" is created when the lower part of the rear of the frame is returned to its original dimension, and thus its original position relative to the toggle stop.
--Dwight
|