G&G UMP Feeding Problem ( shoots 2 bb at the time )
 

Hi, I got a UMP 2 months ago, but got some problem with shipping and fitting battery so... now, today, got my batt from WGC. Works just fine, but found out a big problem when I shoot with my UMP.

Shoot 2 BBs at a time. In semi and Full.

Can anybody help me on this one ? That would be very appreciated.

First time I got a UMP so... don't really know what the problem could be... !?

Thanks in advance ! :salute:

It could be due to poor engagement between the tappet and the sector gear.

Apparently, G&G had issues with their first tappet and released a "new and improved" one last fall. I worked on one last Sept. and the fellow got about 1/2 of a mag out of it before it failed. As it turned out, the tappet wasn't broken as initially suspected (the nozzle didn't move during the firing cylce) but rather the sector gear was shimmed so that it bypassed the tappet entirely. It did engage enough of the tappet to work for about 40 rounds before it wore a groove in the tappet and then failed to engage it.

All I had to do was to re-shim the gears for a proper sector gear/tappet engagement and it's been running ever since from what I hear. I did have to re-use the tappet as no replacements were available at that time, but so far so good.

But this did require a complete teardown of the gun and mechbox.

And while you're in there, remove the lithium grease from the cylinder. It'll save you from the other G&G problem of too much resistance to piston movement and the resulting stripped piston.

that was mine, and yeah what he said, has worked flawlessly... and it was exihibiting the same symptoms as you describe, and then it soon quit all together after the 2bb thing.

Thanks ! I'll try that ! Give you updates after ! Out !

BTW, it's a version 3 I guess ? Mechbox I mean...

Yup, most likely, the STAR one is a v3, the G&G should be too.
Unlesss the G&G followed a different design. Get the gun to a doctor and take a look at the gearbox when he opens it.

It's a version 3 with some subtle differences, mostly in the selector system.