Air nozzle issues

[Hudson]

I'm currently having some feeding issues with a Jing Gong G3, and they're centered around the air nozzle & hop unit.

I'm a passable tech, but nothing amazing.

I can do the basics but this has got me a little puzzled.

The stock nozzle in the G3 is 21.51mm

According to what I can find online, I've seen other lengths stated for G3 air nozzles, usually either 21.20 to 21.3mm, however with the stock nozzle, and with it fully forward there still seems to be a gap between the front of the nozzle and the rear of the bucking of around 1mm or just under.

My questions are:

1. What should the ideal distance look like between the front of the air nozzle and the bucking lips? Should they be right up close together, or have some space between them?

2. What would be the symptoms to look out for of having either too long, or too short of a nozzle? (Obviously if it's much too long, then there'll be no feeding at all, at best)

I've got another JG G3 I've been working on, that also seems to have the slight gap in the nozzle/bucking point but seems to be shooting okay, and even with Said gap, on testing for air leaks with a sheet of paper & a thin cloth there's no movement of them on firing.

This isn't a problem I usually come across, only with these G3s, so it's giving me a bit of an issue so far.

Any help much appreciated, thanks!

 

[Sewdhull]

The nozzle must insert itself into the lips at least a little to create a seal and in my guns the nozzle penetrates the lips enough so that they are past the taper of the nozzle.

You'll get misfeeds and air escaping into the magwell if the nozzle and lips aren't working right.

Different hop units and buckings sit differently and hop units in particular can be sized differently than an original for example and need longer or maybe shorter nozzles.

 

[Hudson]

The nozzle must insert itself into the lips at least a little to create a seal and in my guns the nozzle penetrates the lips enough so that they are past the taper of the nozzle.

See, that's what I've always thought it should be like, before this.

Currently, the BB is just getting stuck in the bucking and wouldn't feed.

On removing the magazine and turning it upside down it then did fire.

 

[Hudson]

Ok, so I woke up early today and decided to tinker with it again before work.

I tested it with the stock bucking & barrel set up and it fed fine, so I went back to the previous one and changed out the bucking. (Was an XT barrel and guarder bucking, now both XT, courtesy of @ak2m4?) and it's running ok, just like the stock set-up; currently coming in at around 1.08J with no hop.

I Still have the slight gap between the bucking and nozzle though, so that's still something I could look at fixing, it'll just take some experimenting to find what length nozzle I need.

 

[Adolf Hamster]

What should the ideal distance look like between the front of the air nozzle and the bucking lips? Should they be right up close together, or have some space between them?

Ideally the nozzle should be pushing into the feedlips when fully forwards.

It may be the case that a given bucking has short or long feedlips too, eg maple leaf macarons tend to be a smidge longer which in some hop units is a prpblem, but the reverse of a shorter feedlip can give the same issue.

What would be the symptoms to look out for of having either too long, or too short of a nozzle? (Obviously if it's much too long, then there'll be no feeding at all, at best)

Too long you'll get feeding issues as even when fully retracted it'll protrude enough to mess with feeding.

Too short you'll get terrible airseal manifesting as low energy (for the spring that's in it) and big jumps shot-shot, this can either be measured at chrono or if you observe vertical dispersion.

It's worth noting that even with the correct length nozzle, if the tip is damaged it won't seal well and give the same symptoms, whilst you *can* shorten nozzles i tend to advise against it unless you have access to the tools to make a clean square cut.

Also worth seeing if the hop unit itself is well secured relative to the gearbox, ie it's not being allowed to move forwards.

 

[Hudson]

The hop unit itself seems ok. Due to the design of the G3 it has an almost fixed position relative to the gearbox, so there's not really any movement back or forwards.

I did try using a small spring or o-rings at the front increase the seal, but this just mostly resulted in feeding issues.

 

[Lozart]

The hop unit itself seems ok. Due to the design of the G3 it has an almost fixed position relative to the gearbox, so there's not really any movement back or forwards.

I did try using a small spring or o-rings at the front increase the seal, but this just mostly resulted in feeding issues.

I have the same gun with similar issues. Following with interest!

 

[Hudson]

I dug through one of my many boxes of bits, and found an Ultimate Sig 550 air nozzle at 22.2mm long.

I might try that and see what effect it has.

 

[Sewdhull]

Invest in a couple of adjustable nozzles which have helped me greatly with fault finding if the nozzle is suspect. Once you have the right nozzle length you can go buy the right one.

Also tappet plates can be bent forwards or back wards at the time of manufacture and/or have mouldings that prevent them going fully forward. You can heat the tappet plates to get them back to 90 degrees and remove the mouldings. Some times the gearbox itself has casting protrusions which catch some tappet plates and not others.

Both my mp5s and g36s have a style of hop unit that locates loosely into the gearbox. I mod mine so that they are better located by sleeving the hop and drilling the gearbox.

 

[Hudson]

I've been looking for some of the adjustable nozzles that I've used in previous guns, but they mostly seem to be out of stock currently!

 

[Hudson]

Well unfortunately the ultimate nozzles I have are too wide for the hop unit, so I'll have to look for something else.

*Edit, called in at BZ Tactical on the way back from shooting, and managed to snag an adjustable nozzle that was supposedly out of stock on the website, so my job just got a whole lot easier! (I hope)

 

[Hudson]

Update: This is not going very well, like I'd hoped!

Still getting the same feeding issues, even going through a variety of nozzle lengths. ?

 

[Hudson]

Well after the last, unsuccessful attempt I decided to change tack and go back to the beginning.

I changed the barrel back to the stock one, and adjusted the nozzle to match the stock length (despite it appearing to still have the slight gap) and that appears to have sorted it. ?

It's putting out around 350fps on an M95, with single figure variance.

At a guess, I think the XT barrel and the location for the C-clip notches might be a large part of it.

As you can see in the photos below there's over half a mm difference in the positions between the XT and stock barrels.

Strangely though, despite having an XT barrel in my other JG G3, that doesn't appear to have the same issue ATM (at least not so far, fingers crossed).

View attachment 134760

View attachment 134761

 

[Adolf Hamster]

Good spot, 0.5mm between the c clips would do it.

 

[Hudson]

At a guess, Do you think replacing the hop unit for a marui version might improve this?

I'm wondering if the JG unit is ever so slightly off spec in comparison, so it works with their own barrels, but not any others.

 

[Lozart]

Thanks, bot.

 

[Lozart]

@Hudson did you ever get a solution?

 

[Hudson]

Just as above really. I've had to stick with the original barrel and air nozzle and it's working fine now.

Looks to just be a design flaw on Jing gongs end.

All the other barrels I have currently seem to be approximately 22.5mm to the C-clip notch, so that's my only option currently.

If I can get a hold of a marui hop unit then I'll see if there's any difference in dimensions that would allow me to use a better barrel, but for now it's doing ok.

Took it out to a game yesterday and it ran fine with no issues.

Currently sporting a new paint job to boot!

View attachment 135726

 

[Lozart]

Digging through the bits I forgot I had - found a TM G3 hop unit. I'll give it a go with an upgrade barrel in my new MC51 project and let you know what I get!

 

[Hudson]

Nice! Keep us posted!

If you have some calipers, Would you be able to measure the TM Vs JG hop unit while you're at it, please?