Fantastic write up !!! Thanks for taking the time to share some of your knowledge !
Thanks for the info. So much history behind it and one has to really dig to find it. This should be in the reference section if it's not already. I have a few questions if you don't mind.
If the mp5's weakness (from what I read) is the extractor spring, what would be the ump's weakness?
Best bang for the buck, what would you buy, USC convert it to UMP much later (long term project, SBR) or mp5?
Would you be doing an mp5 armorer course in the future? For civilians.
As a simple blowback weapon, vs. roller delayed blowback (MP5 series), you get much more of a "jackhammer" effect when firing. You have to be much more focused when shooting the UMP on full auto, in any caliber, then you do with a MP5 series. It is much better suited for single shots or two round bursts then 5 to 8 round bursts like you can with a MP5.
As for reliability, they are excellent. Much looser tolerances and simple to maintain. It is an excellent choice for maritime ops or adverse terrain operations.