Extremely innacurate GBB

[Big Jilm]

I've got a HPA'd WE M4 with a Lambda 6.03mm barrel and maple leaf bucking, and im getting grouping at 15m that could be measured in feet instead of inches.. I seem to get a couple shots that are relatively consistent and on-target, then some insane flyers that go left, down, up and right, in other words inscredibly inconsistent.

I'm a bit lost on what to do, the barrel is brand new and clean, and I've tried both a maple leaf and 4uantum bucking/nub. Only thing I can think of is that I have an NPAS that I put a small dab of glue on the threads to stop it from unscrewing but how could this be affecting my accuracy?

Any help would be appreciated!

 

[Enid_Puceflange]

Hello and welcome.

Firstly, what fps are you getting?
What weight bb are you testing with?

 

[PiratesARRus]

One thing worth trying is adjusting the npas as they can do some magical things at the edges of their range that even a quarter turn can fix.

Also worth checking if the inner barrel has any wobble to it if you haven’t already but I wouldn’t expect that to be the issue if your at least getting some consistent shots.

 

[Tackle]

I don't know about gbbr or hpa, but I agree on checking the npas, which to my understanding is a power adjustment valve ?, as power fluctuations would have the effect your describing.
If you've got a chrono, maybe consider taking some readings before touching the npas, see if there's any consistency in the output power.

 

[Big Jilm]

Hello and welcome.

Firstly, what fps are you getting?
What weight bb are you testing with?

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Thanks, I'm using .30g Geoff BBs and getting between 1 - 1.1J last time I tested. I'm going to try with some 0.28g BBs I have to see if the issue is the ammo but I know Geoff's have a good rep so doubt they are the issue

 

[Big Jilm]

One thing worth trying is adjusting the npas as they can do some magical things at the edges of their range that even a quarter turn can fix.

Also worth checking if the inner barrel has any wobble to it if you haven’t already but I wouldn’t expect that to be the issue if your at least getting some consistent shots.

Click to shrink...

Well it is almost maxxed out to be fair, issue is I've epoxied it closed

 

[StoveCap]

To my understanding HPA'd GBBs should use the pressure regulation to adjust power not NPAS'es, If you have a spare BCG or nozzle I'd try with those but if not the first thing I'd try is the stock rocket valve. If that fixes it then you know its the NPAS. Apart from that perhaps you've reassembled the hop up wrong in some way?


Only other question I'd ask to diagnose is did the gun produce the same inconsistency when stock?

 

[MistakenMexican]

Well it is almost maxxed out to be fair, issue is I've epoxied it closed

Click to shrink...

Replace the NPAS with a normal floating valve for a WE GBBR and that will fix a lot of your problem straight away.

NPAS’s are notoriously unreliable at the very extremes of the adjustment. And if you’re using HPA, you don’t need an NPAS anyway.

 

[Adolf Hamster]

To my understanding HPA'd GBBs should use the pressure regulation to adjust power not NPAS'es

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It'll be situational.

If you've got a low limit then dialling the feed pressure low enough to meet the energy output will mean you've got too little pressure to cycle the action properly.

You get the same issue even with the solenoid engines which is why low flow poppets are a thing to let you run a reasonable pressure for cycling without the gun being too spicy.

That said, in this case it seems like shimming a static rocket valve to the ballpark of your desired energy then using the reg to fine-tune energy would be better than trying to use an npas.

Edit: also worth looking at the bucking, if its the type with the metal c clip try removing that. I have found that can make for too tight a clamp around the nozzle meaning it'll sit slightly out of battery. This means the seal between the mag vent and the nozzle is insufficiently tight and some combination of those features will give an air leak and resultant inconsistency.

I also have a memory that the we buckings are a touch longer than standard ml, you'll be able to see that if its sitting a bit short in the hop chamber which can give the same poor air seal issues.

 

[Big Jilm]

Replace the NPAS with a normal floating valve for a WE GBBR and that will fix a lot of your problem straight away.

NPAS’s are notoriously unreliable at the very extremes of the adjustment. And if you’re using HPA, you don’t need an NPAS anyway.

Click to shrink...

That would explain why my FPS is all over the place, some BBs fall super short and some seem to over-hop. I think I'll try setting the NPAS back a bit and put some teflon tape over the threads to stop it from budging, hopefully that'll sort some of my issues without having to buy any new bits!

 

[GiantKiwi]

And if you’re using HPA, you don’t need an NPAS anyway.

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Yes you do, especially with WE's - The system itself running on bare minimum PSI (120 for it to cycle without fucking up) will output at around 1.8J minimum.

OP, are you using the old style floating NPAS or the drastically better RATech Magnetic NPAS Nozzle?

 

[Big Jilm]

Yes you do, especially with WE's - The system itself running on bare minimum PSI (120 for it to cycle without fucking up) will output at around 1.8J minimum.

OP, are you using the old style floating NPAS or the drastically better RATech Magnetic NPAS Nozzle?

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I'm using an older plastic NPAS, I've unfortunately not been able to find any of the RATech ones for sale in the UK to replace it with

 

[GiantKiwi]

I'm using an older plastic NPAS, I've unfortunately not been able to find any of the RATech ones for sale in the UK to replace it with

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What plastic NPAS - NPAS' are historically made from metal? The Josef Mucha thing? (If so, theres the problem).

WE stuff is now almost exclusively ordering from HK or Taiwan, now that Milspec has basically evaporated from existence apart from the occasional brief stocking once every blue moon.

Get one of these - https://ast-gun.airsofttaiwan.com/i...81&manufacturer_id=13&page=11&product_id=2641 - critically the plastic one, do not buy the aluminium one.

 

[Austeyr]

What plastic NPAS - NPAS' are historically made from metal? The Josef Mucha thing? (If so, theres the problem).

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Not sure if you meant specifically WE NPAS's but the majority of NPAS's I've encountered (VFC/TM) have all been plastic aside from the RA-Tech one

 

[GiantKiwi]

Not sure if you meant specifically WE NPAS's but the majority of NPAS's I've encountered (VFC/TM) have all been plastic aside from the RA-Tech one

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WE specifically, given its about a WE. There has never been a commercial available NPAS for the WE system in 15 years, that was made exclusively out of plastic.

Josef Mucha thing is literally taking a stock rocket valve and melting through it and then putting a grub screw in it - its fine in a pinch for a temporary fix, but its not a long term option as its threading into shitty plastic across a layered structure that isn't meant to have a thread in it, and when it fails, you usually find out because the grub screw gets ejected out the front at 9J+.

 

[Tackle]

the grub screw gets ejected out the front at 9J+.

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Someone will definitely take that hit

 

[Big Jilm]

WE specifically, given its about a WE. There has never been a commercial available NPAS for the WE system in 15 years, that was made exclusively out of plastic.

Josef Mucha thing is literally taking a stock rocket valve and melting through it and then putting a grub screw in it - its fine in a pinch for a temporary fix, but its not a long term option as its threading into shitty plastic across a layered structure that isn't meant to have a thread in it, and when it fails, you usually find out because the grub screw gets ejected out the front at 9J+.

Click to shrink...

I got this NPAS second hand with another WE gun I used to have, so admittedly I have no idea where it's come from, or how old it is, but the main body of it is plastic whilst the 'screw' element is metal. I guess it's pretty old then?

I've added some PTFE to the threads to hold my adjustment in place, and backed the adjustment up, I'll report back if that works or not!

A quick diagram of what I have:

 

[GiantKiwi]

I got this NPAS second hand with another WE gun I used to have, so admittedly I have no idea where it's come from, or how old it is, but the main body of it is plastic whilst the 'screw' element is metal. I guess it's pretty old then?

I've added some PTFE to the threads to hold my adjustment in place, and backed the adjustment up, I'll report back if that works or not!

A quick diagram of what I have:

View attachment 41950

Click to shrink...

OK - someone has used the really, really old RATech NPAS not meant for WE's in it, as the only ones of that design which ever had plastic in them were for WA's - can't just fit any of them in, they're all fractionally different.

RATech themselves even understood the error of their ways and rectified that, but even that was more than 15 years ago. That type is basically useless as the threads wear out over time, and for how old that has got to be, its effectively pissing into the wind. Realistic working life of even the completely metal old style RATech NPAS was about 1-2 years before it needed replacing, as shitty zamac that doesn't hold a thread well, constantly being readjusted doesn't last long.

Magnetic type I linked is notched, so once the setting is made it doesn't back out over time (I was skeptical at first because the experiences of the old design, but the first one I fitted almost 3 years ago now, hasn't been adjusted since I originally set it at 1.1J).

 

[GiantKiwi]

Actually, another thing comes to mind on HPA - assuming you're using an adapter, which adapter and what mags?

The problem of inaccuracy/inconsistency may only be being exacerbated by the NPAS, stem of the problem may lay elsewhere.