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Discussion Starter · #1 ·
Last time at the range the UMP started "acting up". It was awfully dirty, so that may have been the issue. I've not had it back at the range since a good deep cleaning to retest it.

Here's the problem......
While in 2 shot burst mode doing 2 chest, 2 head drills it was actually running 3 shot burst sometimes. I'd squeeze the tigger once and after the second shot I was transitioning to the head shot and a third round would fire usually hitting low to mid neck.
Also while in SA only I was getting an occasionaly 2 round burst.

Could this be due to being dirty, or is it more likely a real internal problem?
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