Hi Mark, you are well on track for total success with the drum mag... That will put you in a very small and unique group!
The little quirks you encounter now, will be both Luger and / or, drum related, but all easy to overcome! In short you are winning!
First of all, the two major weakness's of the Luger to drum tuning process, are, weak main springs, and / or weak extractor springs... Don is correct in that some brisk and firm treatment of the toggle is needed on the first, and in reality, most all of the rounds past 13 to 15... You are going to have to briskly tap the toggle train home on the first round every time... Remember, everything is at the very extreme of their design parameters... any little thing can stop the whole circus... As for the drum mag itself, you are most correct in that the more it runs, the better it gets... but you can also help it by polishing any little areas you feel resistance or rough feeding etc. etc. Dremel makes a perfect tool for this and you can't polish it enough!!
... what ammo did you use?.... just curious... As for the grease, I am now sending the drums out with the inside coated with Dupont dry lube with Teflon and have had excellent results.. I also have had good results with the red grease. A member used Gen. Elect. elect. motor grease and that sounds like some slippery stuff!! I am going to use the DuPont dry lube in tandem with another , red grease, or the GE grease specified previously... Please let us know what you think works as we are still chasing down small issues and nothing is written in stone on these?...
.... Best to you Mark, til...lat'r....GT