Double feeding
 

G&G M4 max double feeding...

Gearbox was never taken apart...
Upper/lower receiver were taken appart tho...

Dont know if the barrel was taken out of the hopup unit since its not my gun...

There is no double feeds on semi...only on full auto...
Anyways my main questions was :
Can mag cause double feeds?

The gun belongs to my friends but the mag is mine :P
That why im asking i have 4 other mags just like this one and they work just fine...

Yes mags can cause double feeding. I assume you are using the highcap that came with the gun?

I would suggest getting some madcaps if that's he case as that might be all you need to correct your issue

No they didnt come with the gun...the one that came with the gun broke..so i bougth 5 JG Hicap mags...I lent it to a guy i play with cuz his mag broke (till he gets new one)
He still has my mag but when he shoots there is always double feeds (only on fullauto).<

Could it be hopup issue aswell?

Im trying to figure out what the problem is..i need to try the mag in my own gun also...

Double feeding is generally associated with the barrel/hop up unit mating. If the barrel retainer clip is cracked, the barrel can slip forward a bit, allowing two BBs to enter instead of one.

also it is possible that the hop rubber's mouth (where the BBs been fed) was worn out which creates a double feeding. that hop rubber mouth serves as a stopper for the BB to feed one at a time during full-auto mode. if this is the case, you will have to change your hop rubber.

What battery are you using? Sometimes double feeding is caused by overspin.

Rack, check chamb... oh no it's not RS :D

Basically the same thing as the ones before but you can also check if the nozzle moves properly : if dirt are crap like that between nozzle and axis it can give enough time for 2 or more BBs to get in the way.
My record was four at the same time... not on my gun.