Internal Modifications
NOTE: This is not solely my own information...it is a compilation of info from previous posts in this thread.
This section is about mods to the internal parts...either to improve durability, tweak performance or modify whatever. I'm not sure that anything in this section is simply a "lego-esque" snap in part and you're done. You've got to understand a bit of what's going on and check your specfic setup.
Adjustable FPS
The following items are ways to alter the nozzle setup to affect the FPS of the rifle. These mods are independant of simply switching gases...which will also affect the FPS of the rifle. Note...the adjustments with most of these to go from 400fps to 350fps are very, very fine...so use a chrony to confirm you FPS before hitting a game.
NPAS
Put simply...refer to RATech's NPAS system. The NP part refers to Negative Pressure...this is different from the WA system that works on a Positive Pressure system. If you want to understand how it works...check out Redwolf's site, they have a great pictoral explanation of "how a GBB works". They describe the action of pistols...but it's the same thing for these GBBRs.
* by far the most popular adjustment system
* works by setting the position of the float valve further forward or back in the nozzle body...further back = more velocity...further forward = less velocity
* well built...machined edges can be very sharp, there's no harm in breaking the edges very slightly (that roughly means take a file and ever so slightly hit all the right angles of the cut outs)
* simple system...sound design
* need adjustment tool...it's a very small allen head grub screw stuck in an L-shaped bar...you can definitely make your own, but until you do..don't lose it.
* need to remove the bolt assembly from the upper receiver to adjust...but that's not too hard
* generally stays adjusted where you set it...but a tiny/little bit of temporary loctite doesn't hurt
* does not come loctite'd together...which is good. But you MUST use temporary loctite for final assembly or else it'll come apart with use.
TCS
TCS was first to market with a consumer add on product that was reported to adjust the FPS. It consisted of a new piston body (usually blue anodized alum), a sqare sectioned threaded rod and a threaded collar to set the position of the nozzle (thus the FPS).
Good theory...didn't work well in practice due to either poor manufacturing, tolerances, or design. The main issue with some of them was that the grub screw in the threaded collar was so small and had so few threads holding it that it could not take many readjustments before it "wore out". Also...it was still necessary to loctite everything in place....so the "quick adjustments" of the system were no quicker than anything else.
* looks nice
* "fragile"/not durable
Mod the float valve
Ways of modding the stock nozzle assembly were the first "home brew" methods of adjusting the FPS. With any Red Green "fixes" like these...the devils in the details and execution. Here's a couple of ways to do it....some are dead simple...others take a bit of work.
1. Insert a spacer behind the float valve. Guys tried using a 6mm solid bushing (CA ones for whatever reason)...slipping it over the guide rod stub that sticks into the nozzle body. This would in essence push the float valve forward "permanently" to reduce the velocity. Some guys would try to epoxy or superglue it in place. The obvious issue with this mod is that it's a fixed setting and it can break loose.
2. Find a nut that fit the threaded portion of the rod that stuck into the nozzle body and use that to essentially have the same effect as the bushing mod above. Loctite or super glue in place. This was more secure...dependant on finding a propper fit...could come loose...fixed setup dependant on the thickness of the nut you find (or you could trial and error grind it)
3. Make a "nut" to fit the threaded rod. I machined mine out of brass and make the threads "tight" so that it'd stay in place. No issues with it coming off...but it's really a guestimate trial and error to get the FPS where you want it. Add in temp variables and it's basically like throwing darts in the dark.
4. "TSC Variation"....thread the stock rod more so it can run up further into the nozzle body (less FPS) or be backed out (more FPS). Place a nut on the threaded rod to jam the nozzle body in place where you set it. Still need to loctite it. Resulted in a fidgety setup that was mechanically more durable than the TCS version....but was still subject to it coming apart with heavy use.
5. "Make your own NPAS valve"...essentially put a screw into the stock float valve. It's simple to tap and thread a hole in the center of the stock float valve. It's also simple to use an appropriate machine screw....grind on a male hex pattern on the end, grind the head down flat to make a plate. It's a bit hard to find the small allen head grub screws....but if you can and have access to a lathe it's pretty simple to knock up an adjustment key. It works...it's solid...you've got to be attentive in making it. I made a couple....I'd rather buy the RAtech one
6. "Make your own float valve"...I machined several out of brass. Different sized inlet holes...different sized bore holes. It works...very easy on a lathe. It's very much a guessing game to get the FPS result you want. Non adjustable...unless you mod it further.
7. "Make your own complete nozzle assembly"....
soon...soon
Nozzle Buffer
Behind the nozzle body, on the rod, sits a small white plastic collar. This collar is ESSENTIAL to the operation of the rifle since it determines the "in battery" position of the nozzle (like headspace in a real centerfire chamber). If it's not there, smushed, crushed...your nozzle will not seal completely and you get failure to function.
I've crushed some nozzles...and I think more than a couple others have too. I think that if you get some jams and you keep pounding away at it (e.g. jamming during a full auto string) that the nozzle basically stops at the plugged up section of the chamber and there's nothing stopping the big heavy bolt carrier from slamming forward...and the stanchions of the nozzle body take the worst of the impact.
So I used some dense rubber material that had just a bit of give to it and cut out a disk to go over the rod in place of the plastic spacer. The thickness is just a bit over the length of plastic spacer....so when the bolt carrier comes into battery it compresses the rubber to keep the nozzle sealed. I haven't had many jams...but I'm hoping when I do the rubber will take up at least some of the shock to the nozzle body and save it from crushing (at least if I switch on my brain and stop shooting after a jam).
The first one I made was a bit crude since I cut it out with a hobby knife...I figured I'd make a nicer one if this one wore out. It's still going strong....so I haven't made another. I figure that a sharp hollow punch sized to the same size as the nozzle base is the way to go.
Changing out nozzles/rod assemblies (Hints and tips)
- loctite and breaking loctite
-
Stop the centering collar from sliding around
- i can easily put my m4 selector to safe, uncocked. no firing issues related to same.
however, i did have a firing issue which was resolved. 'twas due to the plastic block
in the bolt that has moved forward a bit that interfered with the hammer. causing the
pin to hit the mag valve half press and bolt didn't reseat. try moving that plastic back all the way to the back. some even removed this. also, both receivers can be put back together with hammer cocked/uncocked. hope this helps.
- crazy glue
- pin it
Well I got everything working smoothly. I replaced the O-rings on the Valve.. Some silicon oil, and everything works nice now.. But on the other hand.. How much play should the Bolt carrier have side to side in the upper? I am beginning to get the pesky AR rattle from.. The bolt it seems.. Anyone else seem to be getting said problem?
Inner Barrels
- rubbers and inner barrels for the WETTI M4 Gen 3 are they the same as AEG or GBBR Specific?