NPAS Performace

Bar1975 · July 26th, 2014, 13:04

Had a couple of questions in regards to the exact performance of an RA-TECH NPAS installed on a WE SCAR Open Bolt

I just installed a Modify Accurate bucking and 360mm TB Inner Barrel and the FPS shot up from 400 to over 450FPS.

So this is where i figured my NPAS would start to pay off... Field limits me to 400FPS however with the NPAS dialed all the way in pretty much (little to no valve opening visible) and can't seem to get the FPS <400..

the modify is doing such a good job i may have to get a different bucking just for a decrease in FPS!!

My questions are:

1. Can the NPAS be closed up all the way and the gun still shoot? if i remove it and close it completely then re-install it will the gun work?

2. Sort of the same question but should there be some of the npas valve openings visible? Due to the way you have to adjust the npas there is no choice but for some of the opening to appear so that the npas can be held onto while adjusting the unit itself

I'll keep playing around it but just wanted some opinions from others with experience

Drake · July 26th, 2014, 14:26

Are you sure you're dialing it in the right direction? Because "all the way" down the gun will cycle but no BB will leave the barrel (i.e., no gas going to propel the BB). Anyway that's been my experience on an M4.

Bar1975 · July 26th, 2014, 16:10

man im not sure whats going on here to be honest.. i have the valve closed almost completly shut.. i can see no holes visible in the valve when i look into the magwell now (into the nozzle)

the damm thing is STILL shooting 415 FPS.. with it all the way open im shooting over 450FPS.. with it all the way closed its 415...

it doesn't appear to me that closing it all the way prevents airflow behind a BB? Just the least amount of air that the npas will allow versus the most amount of air

are they supposed to not shoot BB's when fully closed?

Drake · July 26th, 2014, 16:25

When I first installed an NPAS I wanted to test what FPS range I could get out of it, so started with testing full open and full closed: full closed the gun cycled but no BBs shot out until I was WTF'ing and lowered the muzzle and the BBs came rolling out.

Check your nozzle for cracks.

siggypoo · July 26th, 2014, 17:41

Don't mean to hijack, but I never knew what an NPAS was for, and this is a really interesting read.
Are they available for a closed bolt We Scar?

Aper · July 26th, 2014, 19:41

OR, did you installed the NPAS with the original valve spring ?

Bar1975 · July 26th, 2014, 20:53

yea i used the original stock spring.. the RA-Tech NPAS doesn't come with a spring.

Bar1975 · July 26th, 2014, 20:55

Quote:

Originally Posted by siggypoo

Don't mean to hijack, but I never knew what an NPAS was for, and this is a really interesting read.
Are they available for a closed bolt We Scar?

NPAS is basically a replacement flow valve in your air nozzle that allows you to adjust the FPS rate buy sticking a little tool (hehehh) into the nozzle and turning to either Increase or Decrease the air flow/FPS

You can pick them up for closed bolt as well

http://shop.ehobbyasia.com/ra-tech-n...l#.U9Q_yHJdV8E

ThunderCactus · July 26th, 2014, 21:15

what weight of ammo are your chronoing with?

siggypoo · July 26th, 2014, 22:01

Thanks tonnes, Bar! I'll continue lurking.

Bar1975 · July 26th, 2014, 22:25

Quote:

Originally Posted by ThunderCactus

what weight of ammo are your chronoing with?

.20's

Npas basically totally closed and still shooting 414ish.... i wasnt shooting that high with a fully open npas and stock barrel/bucking..

i like it when upgrades actually work!

Kos-Mos · July 26th, 2014, 23:20

You changed your barrel from a 256mm 6.08 to a 360mm 6.01.

What did you expect to happen?

You get about 20 fps from the tightness.
You get an extra 20-30fps from the longer barrel.

This is not AEG. Every change to make to the barrel/gas system is exponential.

There is really no easy way to dial down the FPS at that point. Maybe installing a closed tube-type valve (similar to the "low power" valve for the KSC/KWA MP9s and MP7).

ThunderCactus · July 27th, 2014, 01:36

Quote:

Originally Posted by Bar1975

.20's

Npas basically totally closed and still shooting 414ish.... i wasnt shooting that high with a fully open npas and stock barrel/bucking..

i like it when upgrades actually work!

Well then you're shooting way over 450 no matter what you do, you were likely over the limit before you upgraded as well.
GBBR's suffer from what we've termed "joule creep".
You'll chrono 380fps on .20s, but you'll be shooting the equivalent of 415fps when using .28s

Heavier ammo is harder to get moving, so higher pressures build up behind it and cause it to ultimately have more muzzle energy than lighter ammo.
With GBBRs you absolutely have to chrono with the weight of ammo you will be using, otherwise the reading is extremely unreliable.

MultipleParadox · July 27th, 2014, 10:21

I think the behaviour he describes is still a bit unexpected despite the modifications

As Drake said, with the Npas fully closed his gun wouldn't even be capable of shooting (cycling and no BBs leaving the barrel)

I experienced this same behaviour with a Kwa LM4, We Scar Open bolt (and aluminium nozzle), and We M4 (plastic nozzle), so it doesn't seems like a gun specific kind of thing

Bar1975 · July 27th, 2014, 19:12

Update guys.. i had the gun out to my field today and the BB's were dropping after 50-60 feet.. i adjusted the hop up but it did nothing..

i 'guess' this is because the npas if almost fully closed and there is not enough force behind BB'?

Weird cause it chrony's at 414FPS .. but the BB"s cant travel 100 feet..

im going to open up the valve and try again.. might have to replace the bucking with something that will help reduce FPS.

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July 26th, 2014, 13:04	#1
Bar1975 Trader rating Join Date: Aug 2012 Location: ON	NPAS Performace Had a couple of questions in regards to the exact performance of an RA-TECH NPAS installed on a WE SCAR Open Bolt I just installed a Modify Accurate bucking and 360mm TB Inner Barrel and the FPS shot up from 400 to over 450FPS. So this is where i figured my NPAS would start to pay off... Field limits me to 400FPS however with the NPAS dialed all the way in pretty much (little to no valve opening visible) and can't seem to get the FPS <400.. the modify is doing such a good job i may have to get a different bucking just for a decrease in FPS!! My questions are: 1. Can the NPAS be closed up all the way and the gun still shoot? if i remove it and close it completely then re-install it will the gun work? 2. Sort of the same question but should there be some of the npas valve openings visible? Due to the way you have to adjust the npas there is no choice but for some of the opening to appear so that the npas can be held onto while adjusting the unit itself I'll keep playing around it but just wanted some opinions from others with experience

July 26th, 2014, 14:26	#2
Drake E-01 Trader rating Join Date: Dec 2001 Location: Montreal, QC	Are you sure you're dialing it in the right direction? Because "all the way" down the gun will cycle but no BB will leave the barrel (i.e., no gas going to propel the BB). Anyway that's been my experience on an M4. __________________

July 26th, 2014, 16:25	#4
Drake E-01 Trader rating Join Date: Dec 2001 Location: Montreal, QC	When I first installed an NPAS I wanted to test what FPS range I could get out of it, so started with testing full open and full closed: full closed the gun cycled but no BBs shot out until I was WTF'ing and lowered the muzzle and the BBs came rolling out. Check your nozzle for cracks. __________________

July 26th, 2014, 16:10	#3
Bar1975 Trader rating Join Date: Aug 2012 Location: ON	man im not sure whats going on here to be honest.. i have the valve closed almost completly shut.. i can see no holes visible in the valve when i look into the magwell now (into the nozzle) the damm thing is STILL shooting 415 FPS.. with it all the way open im shooting over 450FPS.. with it all the way closed its 415... it doesn't appear to me that closing it all the way prevents airflow behind a BB? Just the least amount of air that the npas will allow versus the most amount of air are they supposed to not shoot BB's when fully closed?

July 26th, 2014, 17:41	#5
siggypoo Trader rating Join Date: Mar 2009 Location: Oshawa, Ontario.	Don't mean to hijack, but I never knew what an NPAS was for, and this is a really interesting read. Are they available for a closed bolt We Scar? __________________

July 26th, 2014, 19:41	#6
Aper E-30 Trader rating Join Date: Jan 2004 Location: Aegiis's Neighbor.	OR, did you installed the NPAS with the original valve spring ? __________________ West Coast EOD Supporter. // Bang One, Bang Em All ! // In war, it's not who's right, but who's left.

July 26th, 2014, 20:53	#7
Bar1975 Trader rating Join Date: Aug 2012 Location: ON	yea i used the original stock spring.. the RA-Tech NPAS doesn't come with a spring.

July 26th, 2014, 21:15	#9
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	what weight of ammo are your chronoing with?

July 26th, 2014, 22:01	#10
siggypoo Trader rating Join Date: Mar 2009 Location: Oshawa, Ontario.	Thanks tonnes, Bar! I'll continue lurking. __________________

July 27th, 2014, 19:12	#15
Bar1975 Trader rating Join Date: Aug 2012 Location: ON	Update guys.. i had the gun out to my field today and the BB's were dropping after 50-60 feet.. i adjusted the hop up but it did nothing.. i 'guess' this is because the npas if almost fully closed and there is not enough force behind BB'? Weird cause it chrony's at 414FPS .. but the BB"s cant travel 100 feet.. im going to open up the valve and try again.. might have to replace the bucking with something that will help reduce FPS.

NPAS Performace

Upgrades & Modifications