I got to thinking about all the after-market parts I installed in my M11/9. On a whim, I opened my well worn copy of the "SWD M-11/NINE Submachine Gun Operating Manual No. 2" to the parts list on page 21. I inventoried the OEM parts that are still in my gun.
Of 57 parts in the OEM parts list, the following 11 are still installed (numbers correspond to part number in the list):
1. Receiver (well, duh)
17. Plate
18. Ejector (rod)
19. Guide Rod
20. Compression Spring, Recoil
29. Grip
30. Grip Screw
36. Trigger Pin
37. Sear Pin
41. Compression Spring, Sear
50. Retainer (spring)
My M11/9 is 19% OEM, and 81% aftermarket. I'm running a Frankengun. I bet most of us M11/9 owners are running Frankenguns. It's amazing that they run at all, let alone 100% as many of them do.
Thanks again to Richard Lage, Vegas SMG, Coffee Freak, Sam from Practical Solutions, Marty from Shockwave Technologies, and this forum for making it possible.