Just measured an unknown m4 nozzle I had (believe it's a stock CA) and it came to 20.68mm (I used a digital caliper).

Yes, it's in place and feels like new. Very strong. The tappet does look like it's either worn or custom however. It's not flat, but has a cut out where the pin on the sector gear hits it and where it hits the shat for the sector gear. I will take some PICS tomorrow when I tear it down again.

No issues at all, the only time it won't go all the way forward is when the gears have move to the point where the pin on the sector gear starts to pull the tapet back. Note that this is the position the gun stops in 99 times out of 100, and is the position it's in when I tear the box down.

Will be checking that tomorrow. I have parade tonight.

I did check this. The bump is clearly visible at full hop, and I can press on the bump with a plastic bar, it doesn't move and stays down with pressure on it. BB stops no problem, and I can't blow it through the hopup when it's on full.

I have learned that I will never know everything about these damn things. For something that doesn't have that many parts, it has more complexities than a fricken woman. :D

Has anyone thought of the spring on the tappet plate? Is it worn, twisted, stretched?

Nice and strong, in my first response above. :D

Actually so strong I think it might be wearing the tappet unnecessarily.

the hopup rubber is what prevents mag dumps. the nozzle blocks the next bb from entering the chamber only while its acting on the round that has already been chambered. when it retracts, it allows one in, and the hopup rubber should stop it. turning the hopup up is not the solution, as the nubbin is downstream from the problem.
if you're getting double feeds, the nozzle is the secondary culprit... the hopup rubber and/or hopup assembly would be the primary. any remaining culprits would be inside the mechbox.... deformed/cracked/malfunctioning or wrong tappet plate or spring, followed by gear or anti-reversal latch problems.

things to keep in mind: the nozzle will not always rest in the same place after firing. where it lands depends on where the anti-reversal latch catches the bevel gear.
you CAN'T have a timing problem if the mechbox cycles - it resets every round.
an improperly sized nozzle could allow a second bb to enter the chamber, forcing a double feed, but a scenario that is more likely would be that your particular mechbox in that metal body combined with that particular front end and that particular hopup and that particular rubber and nozzle is causing an excessive gap, allowing double feeds and mag dumps.
you see, the one thing that TM had going for it was that those plastic molds were the frikkin same every single time, and they had their mechboxes dimensions down to a science, so these problems never existed untill foreign parts were intorduced into the mix. now you have this metal body, that metal front end, some other hopup with an aftermarket rubber and endless combinations of aftermarket mechbox parts that combine to make one big headache.
Looking back at your problem, the solution seems simple. get a brass barrel, and a bag of bb's. load a bb and put the barrel in your mouth. aim and blow hard. this should provide more consistant results.
:D

LMFAO!

Roger that brother. It's obviously a sick gun, so I will fuck with it till I get it working LOL.

Two blown bearings, causing all sorts of fucking havok. It's my own fault. I missed it on my initial inspection because I thought I knew what was wrong with the gun, I narrowed my inspection and didn't tear the box down completely. I actually did'nt know the bearing was blown till I was setting the gear down and dropped it about 2 CM to my benchtop. Fucking ball bearings when everywhere.

That's it. This is the third tme bearings have blown on this fucking thing. Back to bushings.

Here is a picture of the tappet. Does this look overly worn to anyone?

http://tactical.blackthornegroup.ca/...cs/tappet1.jpg

http://tactical.blackthornegroup.ca/...cs/tappet2.jpg

ya thats done dude!

here took a pic of a used one i had....

http://i539.photobucket.com/albums/f...appetplate.jpg

Looks more "fucked with" than worn! Lol, that's very likely the issue you are having. And bearing bushings suck huge ass!

Worn, yes. Enough to make the gun not work? Probably not.

I wouldn't say that the part i circled prob wasnt loading the bb's right.

http://i539.photobucket.com/albums/f...ar/tappet2.jpg

What size of bearings are they and what type of spring are you using?

7MM and no idea on the spring. It's got tighter rings at one end, and is baby blue.

Do you know what fps it's shooting?

OK. Went to bushings and a new tappet plate and guess what? The damn thing works. I just need to re-shim it so it's a touch looser and I will be good to go.

Oh and to everyone in this thread that stated that the nozzle doesn't stop the BB"s from entering the hopup, it does on both our guns (once they are working properly :D )

Just like in this animation:

YouTube - version 2 gearbox animation