"I don't think Hans and Franz sat around all day at the Mauser factory hand fitting magazine geometries to the various calibers of guns they produced." They didn't. All that work was done on jigs and fixtures using multiple steps with machine tools. The factories were set up to produce thousands of identical actions. When a gunsmith modifys a feeding system - that's done one at a time.

copperlake: check your PM's. I found an article that has some useful information that you might be able to use.