TM Sig 552 Air Nozzle Causing Double Feeding
 

Ok, so I've had this problem for a long time but I havnt played airsoft all winter so I havnt bothered to fix it. On my Sig it has been double feeding every other shot on semi auto, and I believe it is because my air nozzle dosn't fully cover the bb inlet. I used a flashlight to light up the bb inlet where the magazine loads the bbs in, and I fired a few shots in semi auto. The starting position of the nozzle is about halfway covering the inlet, upon pulling the trigger the nozzle moves forward the rest of the way to cover the whole bb inlet and then resets to its previous position. Now I'm no expert but I'm smart enough to know that something is seriously wrong, but how can this be remedied. I'm using a guarder Sig series air nozzle (I checked it, its the same length as the TM one), a guarder steel cylinder head, and a stock TM hop up unit. I upgraded carious other parts too but I dont see that as being a problem. I'm thinking that the problem is either coming from the hop-up unit, the nozzle, incorrect timing of the gears, or could it possibly be a bad shim job?(this was my first time shimming a gear box). Any advice would be greatly appreciated.

I have seen this on some other Ver. 3 guns before. It is caused by the resdual intertia of the bevel gear (with two anti-reversal latch hooks). If you install another bevel gear with 4 or 5 anti-reversal latch hooks, double feeding will be gone.
My $0.02

Good info, will keep it in mind to try out next time that problem passes my bench.

so you think if I install something like http://www.wgcshop.com/pcart/shopper...ts%20for%20AEG
the nozzle will return to the proper condition?

Is it also possible that if I over shimmed the anti reversal latch is missing the grooves all together? It seemed that for the first thousand or so rounds the gun was operating fine, but after that the double feeding started along with the gun not feeding in full auto. The full auto problem was solved by installing the original tappet plate.

Is it an aftermarket nozzle? check that your nozzle is proper type and length and can slide in and out of the hopup unit first. This will affect your feeding in any mode.

Anti-reverse latch doesn't need to be shimmed the latches on the bevel gear are wide enough to allow little lateral movements.

Assuming the rest of your gun has stock TM parts in it right now, replacing the bevel gear as mentioned above should solve your double feeding problem. (preferably the same brand and type as the rest of your gears.)

Some tapplet plates are a little thicker than the TM and so they may not be able to move freely in the groves (especially in those reinforced V3 mechbox). You can test this by simply pushing the nozzle in toward the mechbox once assembled and see if the tapplet spring is strong enough to over come the friction. If that is a problem you could just sand or exacto the edges of the tapplet plate down. I personally don't see any huge benefit of aftermarket tapplet plate.

I'm not too experienced with aftermarket tapplet plate. But this I can say for sure: stock TM tapplet can handle operations at near 450fps.

Does systema make a bevel gear with multiple latches, I looked quickly and didn't see one

Incase anyone runs across the same problem, I did infact install a set of gears with 5 anti-reversal latch hooks and it solved the problem 100%.