[yellowmonkey]

Sounds like either a problem with the piston slipping away from the gears or some kind of weird electrical broblem.
Are the cycles on auto full ones (do they take as much time as the semi auto ones)?

[azsarge]

A) might be a nozzle problem

B) Maybe you need to lube the feed chamber a bit.  

If it fires in semi- just fine, that's probably because the BB has time to work its way up the feed tube.  Put some silicon in the feed chamber and fire it in full.  If it works, take the mag out and clean your barrel good with the included cleaning rod and a HOPPES pad or a square cut from a coffee filter (to get the silicon out of the barrel, which will affect your accuracy).

That's my guess.  If that doesn't work, I'd have to see it.  Harley, Crow, et al will be able to help you better.  

However, if it cycles fine in full (and no bb's come out), it's probably NOT an electrical error or gear problem.  In this case, it could be something with the nozzle/tappet plate.

[PyroManiac]

heres an idea...are you using a high-cap? all MP5 hicaps tend to start sucking. mine broke and 2 of my friends broke! if you are using a hi-cap flip the gun up side down and go "bren style" on full auto just to make sure its the mag.

[Harley]

Does it do this with all your mags or just one, have you tried other mags?  Your mags might need cleaning and or lubing.  What size battery are you running?  It could be the full auto is cycling so fast that the mag cannot push the BB's up fast enough to keep up with it.  Try a smaller battery like an 8 volt 1500mah.

[PyroManiac]

ive tried it with one of my friends mid-caps and it seemed to work fine. thanx for the advice tho.

[ikari]

i have used 2 high caps and 1 normal and they all do the same.  the cycles are all the same speed.

[ikari]

oh and i have put tons of lube into it mags/barrel/loading/hopup and shot enough that that lube wouldent effect it.

[ikari]

i have a TM mp5 SD5 (the full stock one).  but any way i got it from a friend who put a  Hurricane Upgrade Kit into it.  but any way it worked great for the first 3 games and then the full auto stoped working.  now it dry fires 3 bbs into full auto and some times shoots 2 bbs after it dry fires.  but i can go into semi auto and fire almost as fast as full and it doesent jam or any thing? any ideas for me on what wrong.