G&G Toptech mp5 firing issue- 1 pull, 2 shots

[Grazzhopper]

Hi guys

Hope someone can point me in the right direction here. I am still new to airsoft and am not too sure where to start looking for the cause of the problem. So as I said in the title I am shooting a new G&G toptech mp5. It was downgraded to a m90 spring by a tech at Toronto Airsoft a few months ago.

Now when I shoot in semi auto the gun will cycle 2 shots per trigger pull. I had the tech there fix it once and it seemed fine for the rest of the day but now the issue is back.

Thanks

[lurkingknight]

what battery are you using?

[Grazzhopper]

Oops, sorry. The recommended 9.6v NiMH it came with and also a smart charger (if that matters or not). I haven't been using a LiPo or any higher or lower voltage batteries.

[lurkingknight]

there's a few things that come to mind...

something called overspin: it's possible that there's so much momentum in the gears that it overcomes the weak spring and it does more than 1 cycle of the piston... either super fast gears, powerful motor or powerful batter or a combination of those 3. This is a common issue in higher powered guns with lower fps springs.

Worn cutoff lever: Depending how soft the material is on the lever or how many shots you've put through on semi this lever could be starting to wear and it's not doing its job of flipping the trigger trolley out of the trigger gate. A second shot comes out because one whack of the lever at the trolley isn't enough to flip it out of the gate.

Or

the mechanical trigger gate posts are too tight together either by wear/arcing or physically too tight and they pinch the trolley too tight so that the cutoff lever (that may or may not be worn) needs more than 1 flip to get it to reset.

Without opening the gun myself, those are the first 3 things that pop into my mind of what can cause a double fire and probably the more common.

Did the gun double cycle when you first shot it with the m90? If it's been doing it since you had the spring put in but not before with a stronger spring, then it's more than likely overspin. I'm not sure how fast the toptech gears are or how powerful the motor is, but any combo of the mentioned 3 can cause overspin.

If it double shotted out of the box with a stronger spring, it may be something wrong with the trigger gate.

If the double shot developed over time, you may be starting to see worn components. A cutoff lever is a pretty common wear and tear part.

[Grazzhopper]

Thanks man, I appreciate the help here.

I had it downgraded pretty much straight out of the box as I got it for the purpose of playing indoors, so unfortunately I have no shooting time with it having the stock spring still in.

Would it be worth trying it out with an 8.4v battery in it or could that damage it?

[lurkingknight]

it can't hurt it.

[pestobanana]

What happens if you pull the trigger very quickly?

[Grazzhopper]

Next time I go I'll take both batteries, thanks.

In regards to quick trigger pulls, still the same effect. I tried with that when I first noticed the issue. So with both and slow trigger action, partial and full pulls I have the result. They did fix the issue for a bit last time I played but then it came back. I have no idea what they did and the tech didn't offer an explanation. I should have asked but I was just eager to get back into the game after sitting a couple out.

[Cobra Gr1]

A worn or damaged hop-up rubber can cause double feeds. Does it double feed on the consecutive trigger pulls or just the first one?