G&G UMP doesn't like it's receiver

[Spike]

Have a UMG with a weird problem. When the gearbox is by itself, it cycles fine. But once I put it in the lower receiver, it's completely dead. No click, complete electrical failure. Occasionally I'll get one shot as soon as I put it in, but it always stops working again. Works 100% of the time when the gearbox is not in the body.

Nothing appears to be obstructing or pushing on any wires.

Ideas?

[mista_t13]

Maybe the motor height needs to be adjusted?

[Kwokwai]

Did you re-shim it recently? The lower receiver might be a tight enough fit that it's squeezing on the sides of the mechbox to cause binding. I had that problem with my Systema v2 box with an original Systema M4 metal body. MadMax helped me to diagnose and fix this many, many years ago.

[sushicake]

Originally Posted by mista_t13

Maybe the motor height needs to be adjusted?

The ump uses a v3 with a motor cage motor heights not gonna matter cause its going to be the same out of the body and in

Try moving the selector plate around also if I remember the ump uses old style tm based selector with the copper band. See if that's not burnt out.