Hi to all! On Luger magazine interchangeability, I have a theory, and it's not much different than any other mechanical interaction design theory? I feel there are two separate realities, and they are simply, what they would have liked to have happen, and the other, is what did happen!
... The first 1900 magazines had a flat fully checkered follower button that screwed into the follower. To the best of my knowledge, the frame was not relived for the, "very soon to be revised" follower button which was staked and protruded more than the first version? All subsequent frames were properly relieved for this button to clear, and there is indication that the 1900 frames were a bit tight right off the assembly line? Anyway, it wouldn't be too hard to assume that all the millions of magazines that came/started shortly after were all made to fit and interchange! That is the fantasy part of the equation! The reality of magazine fit, function, and production paints a very different picture, I will try to explain. Lets start with the pre WW2 magazines which are folded sheet metal and usually sport a walnut bottom. These magazines are made from soft easily formed sheet steel, and as a result will not tolerate and abuse, and barely withstand use? The WW2 war time mags were a bit more robust, but still suffered from soft materials that could be easily formed and machined. The problems were many and they tried to improve the magazines all the way through production? Twisting in the seams, dents, bullet setback deformation, rust and dirt were all enemies to the mag and most show it? And that is just the mags!
So, lets assume they were well aware of the issues with the mags? The only way the could ensure fit and function was by holding very close tolerances just as all German factories did right up until the end! Not only with the magazines, but with the Lugers as well. In our case we are concerned with the magazine well it's self! To be truthful, they didn't hold this process tolerance as close as they should have. You can take a magazine out of one Luger, and it might not fit in another? The only variable that changed was the fit in the mag well????
Through many, many repairs I have found that magazines measurement from front to back should be minimum of 1.098" to 1.102" max. and the mag well on the Luger should allow the mag to drop free in this range. If the magazine is 1.106" it will drag, if it is 1.108" it will be tight. So we have a mag to mag well clearance of, (best combination possible) of .010" max, most are several thousands under that with right around .006" being the average in my hands... Try as they might, they could not keep this tolerance with any real consistency throughout production. That is why i feel they numbered the mags in the first place, and you would know with some confidence at least the mags that came with your gun, would simply fit!!!
I know this is all theory from the hobbit workshop, but it has been acquired thru hands on experience both good and bad, besides, I'm not smart enough to make this stuff up!...
...... Best to all, til....lat'r....GT....
