[Zippaks]

Hello everyone!

I own Cyma 701b-u - basically the Taiwangun's upgraded reinforced version with 90degree trigger etc... 3J - 0,40's. I installed Maple Leaf hop up chamber, with ML inner barrel and 85 MR.Hop. What I am having as a problem now - on random basis I am loading 2 BB's and that happens only with heavier BB's so I am thinking could it be the BB stopper spring too weak?I tried different mags. I removed any kind of wobbles and smoothed our the bolt pull - custom o-rings, whole sleeve, polished. It's butter smooth.

Any ideas to try?

 

[Greendore1]

Ditch the ML hop up chamber and replace it with the action army red instead.

 

[Zippaks]

Ok so I only double feed if I pull the bolt slow. If I pull it faster(just normal) I don't get double feed. Of what I understand I see the Nozzle end is like stairs

and when I pull it slow maybe the BB just hits the last stair and goes inside chamber. I tried putting extremely strong spring on the BB stopper but it doesn't make any difference. I am waiting for ML mag to come. I think it's just the end of the mag that will make difference I am not sure but will update.

 

[Drakker]

If you push the magazine up with your hand while you slowly close the bolt, does it still double feed?

If the inverted U piece or its spring isn't the problem, usually its the magazine sitting to low, leaving enough room for the BBs to move in front of the nozzle. As the first BB is pushed forward, the second BB gives it a push too and take its place before the nozzle is done going forward.

 

[SiliconeSword]

Maybe round down those steps with varying grits of sandpaper?

 

[Danmooji]

Turn the gun upside down, put two bbs in the chamber, and load it.

It's a BB stopper problem with a high probability, so check the head nozzle carefully

 

[Zippaks]

If you push the magazine up with your hand while you slowly close the bolt, does it still double feed?

If the inverted U piece or its spring isn't the problem, usually its the magazine sitting to low, leaving enough room for the BBs to move in front of the nozzle. As the first BB is pushed forward, the second BB gives it a push too and take its place before the nozzle is done going forward.

I am pressing the magazine as much as I can (it's sitting pretty tight even without applying pressure) Also the 1st BB is going inside while I pull it slow not when i push forward. I tried pulling faster and push slow 10/10 no doublefeed THEN I tried pull slow and push fast 10/10 it double feeds so definitely something is wrong while pulling.

Maybe round down those steps with varying grits of sandpaper?

Ahh that's a no-no It would be better if I just buy the ML nozzle

Turn the gun upside down, put two bbs in the chamber, and load it.

It's a BB stopper problem with a high probability, so check the head nozzle carefully

Turning the gun upside down while loaded with 2 bbs - when pulling slow - doublefeeded, when I pull faster - no doublefeeds