NPAS Quick Installation Guide:
You will need a punch kit that goes as small as 1/16".
Remove bolt:
Punch out this pin at the back of the bolt. Be mindful of the direction you punch it out. It should come out easily after a few taps with the hammer on the punch tool. If it doesn't, tap from the other direction. This pin holds one end of the spring connecting to the nozzle.
See how the pin is kind of textured at one end? You want this end to be coming out.
Next, unscrew the two screws on both sides of the bolt. One of them is located here:
These screws act to pull the nozzle out of the hop up as the bolt cycles and prevents the nozzle from extending too far out of the bolt and overly stretching the spring.
Ok. Slide out the nozzle from the bolt.
In the middle of the nozzle, there's a pin that holds the two halves of the nozzle together and also secures the other end of the spring. Pop this pin out. It's small so I usually use the tip of a small nail and gently tap with the hammer. I believe this pin can come out in either direction.
Ok. With the pin out, you can now pull the nozzle apart. Be careful. Don't go crazy because there's stuff in there. There's a spring and a valve. Keep the spring. You won't need the valve anymore.
Here's a comparison of the stock valve and the RaTech NPAS valve.
Although they look the same in size, it is not a drop in replacement. Unfortunately, we actually have to mod the rear half of the nozzle to make this work. Fortunately, the mod is simple. You will need a sharp box cutter knife or exacto knife. This mod should take no more than 2 mins.
First, let's have a look at my crappy pic of the rear part of the nozzle:
On the left side of this picture you will see two raised tabs. The valve normally sits on these tabs. The reason why it's raised is to allow gas to vent into the rear of the bolt. It's important that whatever mods we do that we allow the gas to continue to vent to the rear of the bolt.
So here's how the mod will work. We are going to cut off those raised tabs. "But that's gonna cut off the gas flow to the bolt!", you say. But wait, you didn't let me finish. We're also gonna carve out some new gas vents too. By the end of the mod, it's gonna look like two raised tabs again, only the rear nozzle is now slightly shorter by exactly the height of the tabs (approx 2.5 to 3 mm).
Do yourself a huge favor and make sure your exacto knife is sharp. The nozzle plastic is pretty strong and all, but with a sharp knife, it cuts like butter. Dull knife? Don't bother with the mod because you'll mess it up and probably end up bleeding to death.
I always start the mod by widening the opening of the vents first. Cut vertically into the plastic with your knife until the depth approximately matches the tabs' height. Do this a few times along the base of the vents. Make sure the depth of the vertical cuts are close to the tab height. Then turn the nozzle onto its side and sink the tip of your blade into the nozzle horizontally where you were making the vertical cuts. Be careful. Don't be a putz and cut yourself! The little plastic pieces should start popping out leaving you with nice clean lines. Do the same on the other side. if you did a crap job, just clean it up a bit. It doesn't need to be pretty. It just needs to work.
The hard part is over. The next part is simple. Just use your knife to cut the tabs away. Don't be an idiot and cut more than the original height of the tabs off. Because that would ruin it and you'll need to go and buy another nozzle.
Apologies in advance for not providing pics describing the above mod. I didnt have them handy but hopefully the description is detailed enough for you.
Ok. Time to put the nozzle back together. Insert the new NPAS and the old spring into the front half of the nozzle like this:
Then put the two halves back together again. It should be pretty logical on how the two halves come together. Place the pin into the mouth of one of the holes but don't push thru yet. We need to align one end of the long spring into position first. Luckily, WE makes this easy to align by making the spring length long enough so that the end loop is in the proper position to push the pin thru when the other side is like this:
Pull on the spring to check if the pin is securing it.
Once that is done, lube up the nozzle o-ring with some silicone oil and gently slide the nozzle into the bolt. We will need to pin the other end of the spring onto the bolt so if it's not already properly oriented, twist the loop so that it will align properly. Again, WE was very thoughtful to make this part easy because all you have to do is push the nozzle all the way in and the spring loop should already be in the proper place in the bolt for you to push the pin back in and secure the spring. You'll need to use a hammer and punch to tap the pin all the way in. Pull on the nozzle to make sure you caught the spring.
That's it. Put the two bolt screws back (recommend using loc-tite), put the bolt back into the receiver, pop the recoil spring into place..... Cock, lock, and your are ready to rock.
As for adjusting the NPAS, you simply slot the NPAS tool thru the nozzle opening in the front. Turning clockwise will increase fps. Counterclockwise will decrease fps. I use a little screw driver to help stop the valve from turning as you use the adjustment the tool. Unfortunately you need to do that because there's nothing stopping the valve from freely spinning inside.
With my mods, I am able to maintain my 430 fps upper limit (on 0.2) and can get a very stable and consistent lower limit of 330 fps which is perfect for indoor CQB.
Anyhooo, I hope this was helpful to you guys. I apologize for the crap pics but oh well.