Piston only returns to battery on every 2nd shot

[FoolAuto]

Hi Guys,

I'm new to this forum (and airsoft in general), and I'm wondering if I could ask your advice?

I have a stock G&P M4 rifle, which I recently swapped the pistol grip on.

On replacing the pistol grip, I noticed that the white piston only returns to the fully forward position after every 2nd shot. The rear of the white piston is visible through the cut-out at the rear of the gearbox, and over a number of shots it will gradually work its way further and further back, until the gearbox fires two successive shots (on semi-auto), and then the whole cycle will start again.

For instance, starting from the piston being in the fully forward position:

Shot 1: 20% of the window is filled by the rear of the white piston.

Shot 2: The the piston appears to return to the fully forward position.

Shot 3: 40% of the window is filled by the rear of the white piston.

Shot 4: The the piston appears to return to the fully forward position.

Shot 5: 60% of the window is filled by the rear of the white piston.

Shot 6: The the piston appears to return to the fully forward position.

Shot 7: 80% of the window is filled by the rear of the white piston.

Shot 8: The the piston appears to return to the fully forward position.

Shot 9: 100% of the window is filled by the rear of the white piston.

Shot 10: two shots are fired, and the cycle begins again.

What did I do wrong when I replaced the pistol grip? I made sure that the gears weren't moved from their original position whilst I had the motor out, and that the motor went back in the same way?

The motor is marked "M120 High Speed". I'm not sure what M1x0 the standard spring is etc. Everything, apart from the plastic pistol grip is as it left the factory.

Any help would be greatly appreciated!

[ReconRabbit]

Re: Piston only returns to battery on every 2nd shot

Did you adjust the motor height correctly? If you have only changed the pistol grip then this is the only thing I can think of as to why your having this problem... Try turning the adjustment screw a half a turn a time and see how it is after each adjustment

[FoolAuto]

Re: Piston only returns to battery on every 2nd shot

Did you adjust the motor height correctly? If you have only changed the pistol grip then this is the only thing I can think of as to why your having this problem... Try turning the adjustment screw a half a turn a time and see how it is after each adjustment

Thanks, I'll give that a shot.

As a separate question, just out of interest, do the gears within the gearbox have to be in a particular orientation to each other and the piston, when the motor is reintroduced? Or does the configuration effectively correct itself?

The reason I ask is that whilst I'm 99% sure that nothing inside the gearbox moved whilst I was swapping the grip over, something may have moved inside without my knowing it?

Thanks again for your help!

[JCheeseright]

Re: Piston only returns to battery on every 2nd shot

this is perfectly normal behaviour for a gun, it's caused by the motor carrying on spinning for a fraction of a second after the power is cut. You can 'fix' (it's NOT broken!) it with an active braking mosfet and the removal of your anti-reversal latch if you really want, but there's no need.

[FoolAuto]

Re: Piston only returns to battery on every 2nd shot

this is perfectly normal behaviour for a gun, it's caused by the motor carrying on spinning for a fraction of a second after the power is cut. You can 'fix' (it's NOT broken!) it with an active braking mosfet and the removal of your anti-reversal latch if you really want, but there's no need.

That's great. Many thanks for all your advice - much appreciated!

[jonny lovegrove]

Re: Piston only returns to battery on every 2nd shot

it's not usually that common on G&Ps due to the fact the ar latch on the bevel gear only has 2 (or is it 3) teeth.

[FoolAuto]

Re: Piston only returns to battery on every 2nd shot

it's not usually that common on G&Ps due to the fact the ar latch on the bevel gear only has 2 (or is it 3) teeth.

If it's the same as my other G&P, it has 2 AR teeth.