NPAS and HPA

[danf1234]

I have 4 TM MWS variants that all have Federal Concepts NPAS valves, but I have gone done the HPA route and bought adapters from airtac. 
question I have is should I change the NPAS valve back to standard as I am seeing a 10 fps fluctuation which I wasn’t expecting with HPA?

 

[Adolf Hamster]

It could be worth trying.

Although you're gonna have X psi requirement to get a good cycle, which might put you over the limit so you'd need some method of dropping it back down.

Shimming a standard rocket valve does the same thing as an npas, and might be more repeatable, or a shorter inner barrel can do the job too (dont worry if it's shorter than the outer)

 

[GiantKiwi]

How old are your FEDA's? This sounds like the old 3D printed resin ones which really, really don't like staying consistent as the adjustment screw has a tendency to walk from them as threadlock can't bind to the resin.

 

[danf1234]

They are the older 3D printed ones yes

 

[LMKipper]

The issue you will have is that you'll often need a fairly high pressure for the rifle to cycle consistently. Airsoft green gas/propane is around 140psi at room temperature, so that's a good place to start with a reg setting, then see if you need the NPAS to bring it down to playable limits.

 

[GiantKiwi]

The issue you will have is that you'll often need a fairly high pressure for the rifle to cycle consistently. Airsoft green gas/propane is around 140psi at room temperature, so that's a good place to start with a reg setting, then see if you need the NPAS to bring it down to playable limits.

Vapor pressure of propane at room temperature of 25 degrees C is 8.3bar / 122PSI

They are the older 3D printed ones yes

Probably need to be removing them then, if you can make them work without the NPAS great, but I doubt it. If you need a UK supplier of a better NPAS, Jaeger Precision makes them as well https://jaegerprecision.co.uk/products/jaeger-precision-mws-npas-adjustable-valve

 

[danf1234]

Just bought 7 Jaeger Precision valves to kit out all my RIFs for HPA