RA-Tech Negative Pressure Air System NPAS for Tokyo Marui / WE Gas Blowback Pistols and WE Open Bolt Rifles

"Works great in my WE-Tech M9 Beretta for lowering the FPS. No problems in ~6-7 sessions so far.

"Installed this in the WE M4A1 Open Bolt. It's great. Wasn't a hard install. (Thanks to a YouTube video by a guy in Britain. It has no included instructions.) Took about 20 minutes to a half hour to install, with just a couple of standard tools. Was able to adjust FPS down to the high 200s with .25s so it was legal at my local indoor venue. It also stabilized the FPS, bringing it to a variance of 15 FPS between shots from the previous 40 FPS variance.

"Works wonderfully on the WE AK-74UN(AKS-74U). You can adjust your FPS to coincide with your field limits.

You must modify the rear half of your nozzle in order for this to work correctly. Basically it involves shortening the nozzle by a bit, this is easily done with a dremel or another rotary tool.

"Indeed it does what its suppose to do. Using .25 bbs I manage to lower the fps for my we g39 from 420+ to maybe around 360 or below with proper adjustment and holds quite well too. Now I can use mine in airsoft field games without over-exceeding their limitations.

"Allows you to adjust your FPS on your WE open bolt rifle from about 300-500. All you need to buy is this and your good. Works just as it should, watch youtube videos to figure out how to install it. It's not hard.

"Works exactly as it should, no fuss, doesn't change during use too, chrono'd within 5 fps at the end of a day of use (could be because of tempurature change) I get these with every WE GBBR I buy, having the ability to adjust the fps is awesome, pure awesome. Installing isn't the easiest thing, but it isn't too bad either, there are videos on how to install it that make it quite nice rather than having some poorly drawn instructions in another language. BTW, mine didn't come with instructions, but I've done several of these and I have it down.

"Works Great to adjust FPS on Open Bolt WE Gas Rifles. I use Gas gun exclusive and i have this installed on all of them. Some modification of the air nozzle may be required depending on what gun your putting it in. Just you tube the installation instructions.

"Doesn't come with any installation instructions; you'll have to plan accordingly.. there are youtube videos out there showing how to install this, and it isn't hard to do. There's no cutting or dremeling like some people say- it's merely swapping one small valve for another- but you need to strip down the bolt completely to access it. Took me about an hour to do, and it shoots fine so far.

"Excellent way to have a gun which can play in both CQB and Outdoor Field.

Pros:
+ Can adjust FPS between 250-440*
+ I find it delivers crisper blowback
+ Has tool for quick adjustments

Cons:
- Occasionally has large FPS variance (up to +/-20 fps)**
- At 'max fps' setting delivers lower fps than stock
- At 'low fps' can sometimes misfeed/sluggish blowback

* tested with 0.25 g bb with stronger floating valve spring, stock plastic nozzle, ratech trigger group and ratech bolt carrier, and 380 mm 6.03 inner barrel.
** fps variance is reduced with stronger floating valve spring