G&P M120 Drop in mechbox problem

[chrising]

My G&P M120 drop in mechbox seems to complete two full cycles when in semi. The full auto works fine and the gun does not jam in "semi" mode when firing the 2 rounds.

Any thoughts?

FIXED - see below for solution

[Shirley]

What?
What's the problem? I don't understand your post.

If it doesn't fire full auto, then you need to charge the battery.

[panzergrenadier]

I think the Problem is that when He fires One shot on semi... the rifle fires two... with only one pull of the trigger... and that full auto works fine...

[m102404]

Does it always fire two or does it sometimes fire 3? In semi, if you pull the trigger quick all the way back and hold it there...do you get one shot? If you creep it back slowly...do you get a burst?

What's happening is that you're motor is torquing up really fast (different motors and big batteries will do this) and basically overspinning the gears enough to cycle through a complete shot and enough to get the piston back and released a 2nd time.

Or.

You cutoff lever is not moving/engaging freely...it's sticking every time your trigger is all the way forward and the first shot jiggles it enough to trip on the next shot.

I've only run into the 1st scenario with light springs, big motor, big battery setups....and the G&P M120 is a pretty stiff (400fps) linear spring. I've run into the latter scenario a couple of times...but mostly on clone guns or mechboxes that have had their AR latches/switch assemblies replaced.

The questions at the beginning will help,

Best of luck!

Tys

[TriChrome]

Try pulling apart the switch contacts ever so slightly. It'll make the power cut off a millisecond sooner which may alleviate your problem.

[chrising]

FIXED

Replaced the cut-off lever with a new one. Seems the one that came with the mechbox was faulty...

Thanks for your help!