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RA-Tech NPAS Bolt Carrier kit for Magna M4 GBB



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Old August 28th, 2009, 22:51   #1
kullwarrior's Avatar
Join Date: Jan 2008
Location: Edmonton, AB, Canada
RA-Tech NPAS Bolt Carrier kit for Magna M4 GBB

Grey is the stock G&P, Silver is the RA-Tech
Background info: RA-Tech Also known as Red Alert Technology (unlike what the current people think these days) is a small Taiwan custom shop specializes in upgrades starting with the KWA m4 whom made the highest ROF. (Sustainable) They’re now focusing on mostly the Magna M4 design created by Western Arms, WE has yet to gain support in RA-Tech. RA-Tech is the only current manufacture who produce fps adjustment device for the Magna M4.

What you get in the box: I would say the package was quite neat, the black cloth certainly makes one feel it’s not cheap stuff, and of course it are not. ($260USD)

If you still don’t know why this bolt carrier is so expensive let me explain, the NPAS Bolt carrier set contains: a CNC Steel Bolt Carrier (only RA-Tech and Prime makes steel bolt carrier currently), an Aluminum nozzle, and a NPAS set.
Long Ver.
See Illusion's Post he did a better job than I did
Short Ver.
The NPAS allows one to adjust the amount of fps, you trade in fps with recoil. In simply put the more the fps the less the recoil, the more the recoil the less the fps.

Usage: --What RA-Tech wants you to do
To adjust the NPAS or fps first field strip the Magna M4, then take the supplied allen key (it’s a specialize one) or a deluxe key purchasable from RA-Tech. It is a clock wise threading aka righty tighty. When you turn clock wise it will increase the fps, vice versa if you turn CCW it would increase recoil. Note make sure when you adjust the fps set it at a point where the feet of the flute valve would not obstruct the airway. If the foot obstructs the airflow, it would not cause blow back and would leads to gas venting out.

Turn the allen key CW for more fps, CCW for more recoil. Basically the allen key and the deluxe key are using flute valve to adjust this
Usage: --What Kull’s experience suggest you to do
To adjust the NPAS field strip the Magna M4 AND the Bolt carrier. To do that, that out the E clip holding the nozzle spring back. After than disassemble the Nozzle, (leave the O-Ring) on the NPAS kit of the nozzle turn CW for more FPS CCW for more recoil. After your done reassemble the nozzle ensure the flute valve DOES not obstruct the air flow. What is the difference in doing this? Well I’ll explain why in the problems in NPAS

Turn the spiky part CW for more fps, CCW for more recoil. Basically the allen key and the deluxe key are using flute valve to adjust this

Disassembled of the nozzle, please remove E-Clip prior to disassembling the nozzle otherwise...


Overall I think this is a great design, in DMR you want more fps but don’t want as much recoil, but more than enough to tell you the bolt is lock open. In home plinking its not the best idea to have 500 fps that would destroy your shooting target (if you want to contain the bb splatter) however you want more recoil for fun.
I have tried on the highest fps as well as the highest recoil let me tell you:
Highest fps: Single shot then gas vents out (if it was Pro-Win mag I could speculate the gun become a straight puller like the British AR-15) FPS is between 500 to 550 at approx 24 degrees.
Highest practical fps: 475 fps: cycles just fine, virtually no recoil, essentially it’s a electric blow back.
Highest recoil: let me tell you I was fooling around and didn’t shoulder it properly (on the bone) pull a 15 shot on auto….OW it was dry firing, Im guess you could not shoot it since the flute valve was block all the gas from going down the barrel.
Highest practical recoil: 120 fps, about the recoil of Colt SMG 9mm on semi, about 1/3 on Auto.

Design Flaw:
There’s two major design flaw with the NPAS it self:
1) The flute valve’s head is prone to breaking, this is the part where the easy adjustment tool use, while one might think this would not affect the cycling, you’re wrong, the head actually acts as a stabilizer for the spring. Without the head, the flute valve is prone to flip and turn at an angle making it useless. I broke two of mine, when I told RA-Tech it was a known common problem, however, like all Asian retailer they don’t offer warranty. How to fix it? There isn’t any, just spend another $30 to get a replacement. How to prevent it? Remember I was talking about disassembling the nozzle to adjust it? The only cause to the severing of the head of flute valve is thru the Allen key. It is putting strain on a point. (just like how you bend a paper clip which eventually will snap)

Example of a broken Flute valve
2) The second problem with the NPAS is the self adjusting ability, let me explain: The Magna M4 features recoil, the NPAS is essentially a screw with a spring attach to it as well as an O-Ring to make it tight. With the two problems combine, the NPAS is commonly subject to self unscrewing, which would reduce the fps. (I actually set one at 450 fps after 4 mags it was 150. Using fresh mag every time to chrono so cool down was not a factor) the fixes for this problem is using blue loctite it works well for me, DO NOT USE THE RED OR BLACK otherwise, lose the A in the NPAS to Negative Pressure System as the red and black loctite are permanent.

Nozzle and Bolt Carrier:
The nozzle is a good nozzle, I have put through about 3k rounds without any problems, and the nozzle solves a lot of double feed, misted or jams. It is the only one that has not reported to break when you use it unlike the plastic nozzle. The trade off? If a unstoppable force meets an immovable object what happens? (Sorry quoting for The Dark Knight) Basically your hop up is most likely to break, If it’s an reinforced hop up like G&P, RA-Tech non-parity, Prime I have no clue what will happen, only thing I can tell you something is going to get damage or break. But overall I think the aluminum nozzle is a great choice as it solves a lot of problem as saves a lot of money in terms on replacing plastic nozzle.
The Bolt Carrier is a not to shabby one in my opinon. The reason why I say it that way was because; it’s heavier than the stock one meaning you will need a stronger buffer spring to have the same ROF. The other problem with the Bolt Carrier is that it is still subject to wear similar to my stock G&P Carrier due to the bolt catch. The only fix that can save the bolt carrier is to use a softer metal for the bolt catch. This also mean that if you plan to use an expensive bolt carrier (especially if its aluminum) down grade your inokatsu or G&P bolt catch to something easier to break. Why am I saying this? (contradicting what WA owner is trying to get away from) A Bolt Catch cost $15 for an RA-Tech one which is good, A bolt Carrier runs from $100 to $260 which is the one we’re reviewing ($260) Which one is cheaper to replace?
I firming believe that the NPAS kit is something a Magna M4 GBBR player will need if he/ she wants a good accuracy as and following the fps limit. (350, 400, 425, 450) The entire bolt carrier kit basically eliminates four of the five WOC problems. (Charging handle snapping is the one it didn’t fix) As for Newer player who support the Democratic People’s Republic of the Marvellous and Glorious China don’t bother, just get a PDI 210mm Barrel. Why? If you want to go cheap why not stay cheap? If you want to spend money you shouldn’t get a Chinese Imitation, WOC is affordable enough (for Americans, for Canadians, if the Metal body of the G&P’s WA m4 cost $450, you will save 200 to build a GBBR from scratch using G&P and RA-Tech parts)
How to Keeping FPS lowered in Kullwarrior’s little world:
The Unspeakable Chinese Magna M4 clone: PDI01 210mm Inner barrel (yes its shorter than CQBR barrel length)
WOC/ WA/ Inokatsu:
***NPAS kit for begineers,
***NPAS kit w/ Nozzle for a person who wants reliability and budget while sacrificing bolt locking back,
***Full NPAS Bolt Carrier for those who wants reliability, budget, and bolt locking back for last shot.

If you were to purchase a NPAS kit, NPAS Nozzle, NPAS Bolt Carrier set my suggestion are:
**Get blue loctite, as soon as you found your setting apply loctite on the screw. If you want to change your mind you can still change the fps
**Avoid using the allen key or the deluxe key to adjust the fps. It might sound bad, but keep in mind you’re not allow to adjust fps in the game field and also the bolt carrier usually have grease or oil on em so its not clean to change fps anyways.

Overall RA-Tech Steel Bolt Carrier with Aluminium nozzle and NPAS Kit: 8.5/10
Reliability: (NPAS, Nozzle, Bolt Carrier) 7/10, 10/10, 8.5/10
Durability: (NPAS Kit, Nozzle, Bolt Carrier) 7/10, 9.5/10, 9/10
Price: (NPAS Kit, NPAS + Nozzle, Bolt Carrier Set) 8/10, 9/10, 8.5/10
Innovation: 9.5/10 (adopted someone’s idea on a forum)
RA-Tech service: High, does stick out above the stores I purchase (Redwolf, UNCompany, RSOV, Ebaybanned aka EBAirsoft)
General rule of thumb for Kull’s rating system:
7/10 average, what ya expect its GBBR its gonna (whatever suppose to happen for GBBR)
8/10 above average, its gonna (whatever suppose to happen for GBBR) but its gonna take a while
9/10 High Its rare that it will (whatever suppose to happen for GBBR)
10/10 Excellent Its not gonna (whatever suppose to happen for GBBR)

Background info for me: (If I’m biased)
This is my first GBB for me, I have owned 2 springers. Most of my info are based on You Tube vids and forums info I’ve learned. (So far all bad thing about WOC are true)
I have never fire a rifle calibre firearm before, I have handle Colt SMG in 9mm in the U.S. fired approx 100 rounds, both in semi as well as auto.
If I’m a acting a lil bit like safety nerd, I apologize. I’ve taken firearms course and holds both PAL & RPAL. On top of that my parents heard horror story and was directly influenced by airsoft in negative manner. (Neighbour’s kid lost an eye cause someone shot an airsoft gun which bb hit his eye, the kid didn’t tell the parent until it was too late)
I consider myself to be Taiwanese after Canadian, and I personally support Taiwan more than Hong Kong, far great than China. (I despise China aka PRC NOT ROC)
I have the G&P WOC for 1.5 month now, The RA-Tech Bolt Carrier has been out of commission three major times (Flute valve broke, Charging handle broke, Nozzle spring broke)

Last edited by kullwarrior; August 29th, 2009 at 16:49..
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Old August 29th, 2009, 15:53   #2
GBB Whisperer
ILLusion's Avatar
Join Date: Jun 2002
Location: Toronto
I don't agree with your description of the NPAS versus PPS.

Both of them work on the same basic principle, in which gas is allowed to flow forward to project the BB, and once the BB moves, the valve then shuts off and 100% of all remaining gas is re-directed to fire the blowback mechanism. It's a 1-2 operation. The projectile always leaves the barrel first, before ANY type of semi-automatic self cocking action begins.
At no point is gas "split" to operate two functions at the same time. That would be inefficient and quite a waste of gas. Even real guns do not operate in this manner.

The difference in the systems, is what happens once the BB moves.

In the Positive Pressure System, the valve is CLOSED in its natural state, and requires a positive pressure against the nozzle in order to open the valve to allow gas to fire through the nozzle. In this case, the BB is the positive pressure, pushing the reed back in order to open the valve. Once gas is fired, gas is continually fired through until the BB is far enough down the barrel to allow the reed valve to naturally close (under spring power), which then redirects all gas power to the blowback cycle.

The Negative Pressure System alters this slightly, by allowing the valve to remain OPEN in its natural state. Gas is fired out of the nozzle to release the projectile, and continues to release gas until the BB clears the barrel. Once the BB clears, the pressure behind the valve builds to a higher amount than what's in front of the valve (in the barrel), and the result is the valve being forced shut. In essence, a negative pressure is built on the opposing side of the valve to cause it to operate. And again, once the valve is closed, all gas pressure is redirected in to the blowback cycle of the operation.

*Most* modern GBB pistols operate through this "negative pressure" concept, with WA being the exception (which is no surprise why this Magna system was based on such a design.)

Last edited by ILLusion; August 29th, 2009 at 15:58..
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Old August 29th, 2009, 16:35   #3
safx's Avatar
Join Date: Nov 2005
Location: Toronto, St. Clair West
Thanks for the info guys, lots of good
info here. And I guess it's only a matter
of time before I join the bolt grinders
club, especially since it's a WA design
Retired Freedom 35
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Old August 29th, 2009, 16:51   #4
kullwarrior's Avatar
Join Date: Jan 2008
Location: Edmonton, AB, Canada
Thanks Illusion you did a better job!
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Old October 16th, 2009, 17:59   #5
808's Avatar
Join Date: Mar 2005
Location: - Winnipeg
Great review.

Thanks kullwarrior!

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