Full auto feeding problems....

[NeilLothian]

Ok so I bought a cheap m7a1 Asia electric. It was giving out around an inconsistent fps around 390 so I decided to cut the spring to downgrade the FPS to 350, but I some how ended up stripping the piston *DOH*. so i have now upgraded the spring, piston, piston head and air nozzle and put in a better hop rubber all from SHS and now the gun fires great in semi, but it blank fires in full auto.

i have tried changing the hop rubber a couple times but nothing. do you thing i need to change the hop unit? i did have a madbull 3 in 1 hop unit from my previous AEG and tried that, but i had feeding problems where the hop unit wasn't in contact with the mag.

I'm now thinking a delayer chip might help, So what's you opinion guys.

: Asia electric m7a1 using a 7.4 lipo.

 

[RR01]

Does it fire cleanly every time on semi? If so then it might be a feed issue with your mag. If it does it with any mag then it's more likely an issue with either the hop unit, the tappet plate / nozzle, or the alignment between the two.

Turn the gun upside down and, looking down into the feed hole in the hop, watch the nozzle move on semi. It should make a full back and forward movement. If it does, then look when using auto. Does it still look like it's moving properly each cycle? If it does, suspect your hop unit isn't allowing bbs to feed smoothly. If it doesn't then check that your hop unit is properly aligned and that it's being pushed fully back towards the gearbox. Did you ensure the spring on the top of the hop unit was in place? I had that problem on a G&G CM16 when I replaced the hop unit and didn't realise the spring had fallen off. The hop just wasn't sitting correctly and gave similar feed issues to your problem.

I had similar issues with Madbull Ultimate hop units. In some M4s / M16s they fitted and fed perfectly. In others they just didn't want to work at all, even in a rifle sporting a Madbull receiver set.

 

[sp00n]

Was the air nozzles the same length?

 

[NeilLothian]

Does it fire cleanly every time on semi? If so then it might be a feed issue with your mag. If it does it with any mag then it's more likely an issue with either the hop unit, the tappet plate / nozzle, or the alignment between the two.

Turn the gun upside down and, looking down into the feed hole in the hop, watch the nozzle move on semi. It should make a full back and forward movement. If it does, then look when using auto. Does it still look like it's moving properly each cycle? If it does, suspect your hop unit isn't allowing bbs to feed smoothly. If it doesn't then check that your hop unit is properly aligned and that it's being pushed fully back towards the gearbox. Did you ensure the spring on the top of the hop unit was in place? I had that problem on a G&G CM16 when I replaced the hop unit and didn't realise the spring had fallen off. The hop just wasn't sitting correctly and gave similar feed issues to your problem.

I had similar issues with Madbull Ultimate hop units. In some M4s / M16s they fitted and fed perfectly. In others they just didn't want to work at all, even in a rifle sporting a Madbull receiver set.

Click to shrink...

I have just checked and it seems that firing semi the air nozzle does it's full cycle(moves forward and returns back) but on auto it seems that the air nozzle is only doing a half cycle (moving forward and only half way back before moving forward again ) sometimes it doesn't look has if its even moving back at all when fully forward..

 

[RR01]

Then at a guess I'd say from experience you have an issue with the alignment of the gearbox and hop unit / inner barrel. If you can, try substuting a different hop unit to see if it still happens. If it does then it might be a problem with the alignment of the outer barrel in the receiver, so not letting the inner barrel sit correctly. Check the D-Ring nut is done up tight.

 

[NeilLothian]

Then at a guess I'd say from experience you have an issue with the alignment of the gearbox and hop unit / inner barrel. If you can, try substuting a different hop unit to see if it still happens. If it does then it might be a problem with the alignment of the outer barrel in the receiver, so not letting the inner barrel sit correctly. Check the D-Ring nut is done up

Click to shrink...

UPDATE: Ok so I tried a few things this morning, new tappet plate and delayer chip, this made this worse (blank firing in all modes) so they were removed, I inserting the old piston head and nozzle and would you believe it now functions ok in both semi and auto. I have now found out this gearbox is different has all ver.2 parts from shs don't fit correctly or make the gearbox worse. I have however tried ver.3/ ak piston head and it fits nicely so I shall try a few other parts such has air nozzle and tappet plate and see how this works out.

Has for the hop up chamber I think I will replace anyway its crap and doesn't function correctly but I think I might struggle to find one that fits has the one I have seems to have a longer bore?( where the bbs insert from mag).