BBS jamming in the barrel. Sometimes just spitting out.

[GreenDragon]

The problems above are constantly BBS jamming in the barrel or if they do Leave the barrel they travel a few meters.

Initially I thought it was the gearbox as I know the piston seals are worn. So I swapped the gear box with my good one. The problem was the same.

The gun in question is a 2nd hand AK it had a metal hop up so I swapped in my CYMA factory fitted hopup and the gun fires .

This now highlights that the upgraded hop up is not working compatible with the gearbox although it appears to be identical to my upgraded hop up in my good AK.

I'm now a little unsure.... Im thinking do I need a longer nozzle? Or is the upgrade hopup machined wrong but looks identical to the plastic factory one .

[Sitting Duck]

no you need a cyma hop & bucking is my smart ar$e reply

 

sounds like bucking lips are too tight - see if you can push a bb through the bucking lips

could also be a crappy/dirty barrel too tight with slightly egg shaped bb's - some really tight barrels will not work with mediocre bb's

as for nozzle - well get nozzle fully forward on gearbox, then place hop unit up against it and you should feel about 1mm resistance as it seals

but to me sounds like bucking lips are too tight or barrel is crap or possible a 6.02mm tbb with crap bb's

roll bb's down barrel - ooh there are loads of trial n error tests to look into

 

hop/bucking is one problem area but it is hard to pinpoint the exact casue coz it could be a couple of problems at one

 

I know it is M4 based but this vid demonstrates some very good ideas & what to look into that apply to other airsoft stuff

seriously watch some of this coz it explains a LOT of what to look for - will give plenty of pointers at least

don't think you need to do any modding - just watch the stuff like check bucking lips etc....

you might need to try another bucking, have found some buckings are great in some hops but in others the lips get pinched

well you get an idea - just watch the damn vid

 

[karl_liverpool]

I had similar with my Marui g3. I had pulled bucking too far on so BBs didn't get gripped right edged it off slightly and it was better just a random less powerful shot. Fitted a new bucking and its perfect now.

[St George.]

Could be your nozzle is not centred in the hop unit ,look insie the hop( where the nozzle normaly sits)look for rubbing marks ,you may be able to pack the hop unit to centre it up.

If the nozzle can't move forward quick enough due to friction,the pistion will fire before the nozzle has sealed with the bucking,and the bb wont shoot at full speed and fall short

[delbert]

What type of metal hop is it, Prowin, if so then I am with Sitting Duck on his diagnosis.

 

I fitted a Prowin to my M4, had the same issues, ended up drilling the center of the Prowin out by 0.5mm as it caused the lips of the hop rubber to be to tight, easy test as other have said though.

 

Take barrel and hope out, drop a bb onto the lips and apply pressure, it should drop through pretty easy.

[cooprey]

i will watch the vid above when i get a chance, not sure if anyone still reading this one but i have a similar issue with a cyma AK, but mine starts miss firing but only after a full days play of auto and semi firing, probably pushing around 4000 bbs through.

 

I have cleaned out the barrel and hop best as i can on site but it still fires only a few meters or the bbs back up in the hop and fire 2 or three at once.

 

i have tried with different mags both hi and mid cap but it doesn't matter, still gets jammed.

 

but the day after if i try it at home it fires just fine, it's as if the hop rubber is getting hot and expanding and stopping the feed?????

 

any suggestions would be gratefully appreciated