Fail to feed?

[mauserk98k]

Hello to all. I am new to the Luger Forum, and I would like to find some help if at all possible with a bit of a strange problem. I have a 1917 Erfurt that I take out to the range from time to time. I have recently encountered an odd problem, it will fail to feed from time to time for apparently no reason that I can find, or that anyone I showed it to could find. (Not that anyone else that has looked has had any experience with Lugers.) It is approx. every third round?

It does not jam, and it will eject the previous case, but it seems to be just missing the next round from the mag. I have noticed that the top of the brass from the missed round has a scuff as if the slide made contact, but did not strip it off. I thought it may be a magazine issue, but it does it with all three of my mags. and they all work fine in my S/42. (my only other Luger) If any of you folks have had a similar problem, or have any thoughts as to what I could do, please let me know. Thanks, Roger