What spring for a stock gen 8 ump45 gearbox


I’m getting a gen 8 Ump 45 from tac edge and was wondering what ‘m’ spring will improve my performance without completely destroying the internals.


I’m sure someone else has a comment about springs for a nylon gearbox, my comment is to focus on the air seal (plunger o-ring, nozzle tip and t-piece) before thinking about upgrading the spring.

Because otherwise you’re putting additional strain on a structure that is designed to be only just strong enough, only to then lose some of that air in leaks before it even gets to the barrel.

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Thanks for the heads up mate.

I’m quite new to all this and I’m already planning on upgrading the o-ring, so that clears up quite a lot.

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There’s plenty of good info on the forums here if you have a click through, lots of guys upgrading their gear and giving feedback on the results. Also, if you haven’t already checked it out, LowGuido’s youtube channel has plenty of videos of the man himself taking apart and servicing/improving Gen 8 gearboxes (I think that’s what is in the UMP?)

That should get you started anyway, it did for me :smiley:

Yeah i found his videos and they are an absolute life saver.

Cheers for all the help mate!!

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