Hopup/magazine/who on Earth knows problem - M16 variant

[axisofoil]

Alright. Another interesting problem for everyone on here. I haven't seen anything like it, searched, didn't find anything too similar.

Basically, I ahve a King Arms Sr16. Shooting around 470fps, g&g green bucking, the king arms hopup that it came with, and an airsoftgi6.01 509mm tightbore.

Here's the problem. Sometimes the gun shoots perfectly, the hopup works just like I tell it to, bb's fly straight, fast, and far.
And then randomly, they will either not feed or instead fire at only around 100fps and kinda just fall out of the barrel.

This is a problem that just started happening, and is getting worse it seems.
It seems like I can get it shooting right most of the time after about 20 rounds into most magazines, although some don't ever work... and occasionally a fresh mag will work perfectly all the way through.

I have tried all sorts of different mags. I have removed and reseated the hopup unit. fiddled with it. punched the gun. told it I was sorry. Everything I could think of.

Any ideas on what would cause such a weird behavior?
If you would like more information, just ask. I will do what I can to answer.

I'm going to try it with a different hopup/barrel combo and see if that fixes it, etc as soon as my finals are over.
But if anybody knows of any problems that cause these symptoms, I would be very much pleased to listen to that information.

[Vince]

Tappet plate or nozzle.

[axisofoil]

Tappet plate or nozzle.

It IS always the simple things I forget to check.

[carbon14c]

had this exact same problem, turned out to be the nozzle.

[Vince]

you don't get to be as pro as me by being wrong

[axisofoil]

you don't get to be as pro as me by being wrong

Well, when it turns out to not be the nozzle or tappet plate, then what?
Because they're both working fine and not broken or worn.

[axisofoil]

Could it be that my sector gear has a dwell clip (the things used to increase the time the nozzle is pulled back...). I recently upgraded the motor and it's cycling a little faster now than it used to. Maybe I'll try throwing an 8.4 in there instead of the lipo and see if that fixes it.

[Vince]

you don't get to be as pro as me by being wrong

Well, when it turns out to not be the nozzle or tappet plate, then what?
Because they're both working fine and not broken or worn.

Is the nozzle seated correctly?

If you already changed magazines, BBs and verified that the hopup chamber is not damaged, the tappet plate and the nozzle are the only things left in the equation.

The only things that impact feeding are things that touch the BB.

The tappet and nozzle are really one unit in practice for this.

Tappet retracts, brings nozzle back.

BB enters, from magazine, into chamber's void made by nozzle being retracted.

Tappet and nozzle forward.

Air pressure, shot.

If you already changed the mags and BBs - what's the fusible link here?

[carbon14c]

axisofoil; at first glance the nozzle didnt even look like it was cracked, but here.. let me try to illustrate the problem


..actually scratch that, i cant find the nozzle. its buried in the trash can  :evil:


basically what happened was, the raised ring that goes all around the nozzle.. (towards the wider end) .. well part of that ring (at least half) was just gone. as if it had been ground down. i mean i didnt even notice it until i actually looked at it real close..


you probably did that though, right?  :lol:

[Vince]

A sector chip wouldn't really be a DRAWBACK, I don't think. At the very most, neutral.

For me, a sector chip fixes a problem and has no effect if you didn't have that problem to begin with.

That being said, I am totally unaware of their operation because I've never, ever needed one.

[Vince]

Echoing carbon14c's statement, I would really inspect that nozzle.

This looks like a classic case of a lack of sealing in the chamber.

I think it's the nozzle and not the cylinder because you get full power shots sometimes, but not all the time. If you got crap power sometimes and crappier power the other times, I'd say cylinder.

Try swapping nozzles.

[axisofoil]

I haven't needed a sector clip... but it was on the gears when I got the gun. I haven't needed to upgrade the reinforced steel gears at all.

The nozzle is seated, and does not move from it's place in the tappet plate. It's holding compression also (piston head through to the nozzle all holds tight), so no cracks. It's probably about time it got replaced anyways though. I have an extra around here somewhere.

I'll let you guys know on thurs night when I have a decent amount of time to tinker and stuff. I'll re-check the nozzle, tappet plate, and everything else that goes bump in the night. Full tear down and relube time! yay!

I will replace the nozzle. and I'll try a different hopup/barrel. Maybe a new cylinder and piston set if that's what it takes to track down this problem. I want this fixed! and I have enough spare V2 parts around to completely rebuild the thing.

Oh, and thanks for the help guys. My pride and joy is sick. Gotta get her up and running again. lol.

[carbon14c]

Full tear down and relube time! yay!

 /


just like PC troubleshooting, long, tedious, and sometimes boring :| lol.

[BATMAN]

Here's the problem. Sometimes the gun shoots perfectly, the hopup works just like I tell it to, bb's fly straight, fast, and far.
And then randomly, they will either not feed or instead fire at only around 100fps and kinda just fall out of the barrel.

It's very possible you could be making this more complicated than it actually is. What you described sounds a lot like a jamming problem.  Not all BBs can make it through a 6.01 barrel with no problem.  It can certainly cause them to get jammed and sputter out the barrel one at a time.  If you haven't tried already, switch your barrel out for one not as tightly bored and see if you have the same problem.  It's certainly worth a try.

-BATMAN

[axisofoil]

Here's the problem. Sometimes the gun shoots perfectly, the hopup works just like I tell it to, bb's fly straight, fast, and far.
And then randomly, they will either not feed or instead fire at only around 100fps and kinda just fall out of the barrel.

It's very possible you could be making this more complicated than it actually is. What you described sounds a lot like a jamming problem.  Not all BBs can make it through a 6.01 barrel with no problem.  It can certainly cause them to get jammed and sputter out the barrel one at a time.  If you haven't tried already, switch your barrel out for one not as tightly bored and see if you have the same problem.  It's certainly worth a try.

-BATMAN

I've tried different bb's.
The first half of the bag was fine. THEN the problems started occurring somewhat suddenly. I've used G&G, TSD, and Goldenball in multiple weight from multiple bags. Same results... so unless my barrel suddenly decided to be less than a 5.95... but yeah, that's one of the things I plan on checking. Just in case.

And again, thanks for your input.