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Reducing FPS in a WA System GBBR


hwagan

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Morning,

 

In the very near future, I'll be picking myself up another WA System GBBR. 

That being the case, I'll need to reduce the FPS on it - I'm aware of the NPAS of course, but the time between picking it up and gaming it won't allow enough days for delivery of an NPAS. That being the case, I'll need to reduce the FPS.

So far, I know of the following methods;

 

Chopping the inner barrel

Clipping the flute valve spring

Heat shrink on the valve stem(?)

 

Now, I'm not going to chop the inner barrel down this time, simply because it's an MRP and I'd rather avoid removing the barrel unless I really have to. 

 

So, that leaves me with modifying the bolt/nozzle/valve assembly somewhere. I've had a good google, but I'm finding a lot of conflicting info and the like.

So far, the safest bet seems to be Akira's flute valve spring mod; However, while theoretically it should work I've not found any evidence of it being done to a WA system. As for heat shrink on the valve stem, that's another foreign object in the nozzle I'd like to avoid if possible.

 

So, the question is; What's a good DIY mod for a WA system GBBR to knock the FPS down to 350 on a hot day? 

 

Any help greatly appreciated.

 

 

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Try switching the propellant...if the power output is way too high, I usually just drop down to 152a. I don't recall ever exceeding 1J using 152 and .25g BB's on my WA M4 (I'm using an 18" ORGA 6.23 and stock G&P negative pressure nozzle). It still operates effectively, but my range goes down and the power output is a bit more erratic compared to 134a, propane, or CO2. However, I do understand that heavily modified GBB's will not operate correctly on 152 since it's generally thought to be a very weak gas.

 

Hope this helps.

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Thanks man, as a last resort I'm going to run 144a (The closest we can get easily), but having done so before, even in hot weather it's a very sluggish cycle speed and the cooldown seems to be a lot more noticeable.

Ideally, I'd like to run it on Propane/GG, but with a fixed maximum output of around 350. I know it can be done, I'm just not sure what the best way to go about it is!

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I see Im fairly new to these creatures. I was planning on making a threaded collar that screws in the nozzel to reduce the flow on mine .Just need to find somting the right diameter ,the inner diameter will be a bit of an experiment as to its out put, I need a chrono realy.

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I see Im fairly new to these creatures. I was planning on making a threaded collar that screws in the nozzel to reduce the flow on mine .Just need to find somting the right diameter ,the inner diameter will be a bit of an experiment as to its out put, I need a chrono realy.

 

 

True, but you're the mighty heroshark, man of technical wizardry with the ability to make things out of stuff! The threaded insert would definitely be a good idea, but I'd worry about the integrity of the nozzle once you've cut a thread into it, depending on how thick the wall is.

 

So far the plan is (I've got a borrowed chrono) to try increasing the size of the valve stem via a reversible method and see if that's a go, if not it'll be the flute valve spring chop job. 

 

If noone posts any surefire/better ideas by tomorrow night, I'll post up my results and a guide on what I've done and the like.

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Yeah, you don't want an NPAS really, they're kind of *suitcase*. I would also be careful with clipping the floating valve spring, I tried it on my KWA MP7 yesterday and it just messed the gun up (luckily I had a spare).

 

Also anything other than propane just costs way too much to be a long-term option. Something in the nozzle/floating valve which keeps the cycle speed and reliability of propane but drops the power is what you (and I! :D ) want.

 

A wide bore barrel is one option (I don't know how hot the WOC shoots), ORGA make extra-wide bore barrels that reportedly make your gun shoot real nice too.

 

Also hwagan would you settle on a GBB M4 already?! :P what went wrong with the WE?

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Yeah, you don't want an NPAS really, they're kind of *suitcase*. I would also be careful with clipping the floating valve spring, I tried it on my KWA MP7 yesterday and it just messed the gun up (luckily I had a spare).

 

Also anything other than propane just costs way too much to be a long-term option. Something in the nozzle/floating valve which keeps the cycle speed and reliability of propane but drops the power is what you (and I! :D ) want.

 

A wide bore barrel is one option (I don't know how hot the WOC shoots), ORGA make extra-wide bore barrels that reportedly make your gun shoot real nice too.

 

Also hwagan would you settle on a GBB M4 already?! :P what went wrong with the WE?

 

 

Yeah, I've heard a lot of that about the NPAS - Ideally I'd like to avoid it if at all possible.

 

Gas wise, I don't mind using Brut (what I use at the moment), but I'll make the switch to Propane eventually! I just refuse to buy it from anyone who isn't called Hank Hill.

 

So far then it's looking like increasing the thickness of the valve stem is the best option; Although I had good results clipping the spring in my LM4 - It took a little bit of fine tuning (clip/stretch/clip/clip/stretch) but it worked out well in the end.

 

A wide bore barrel is an option indeed, but the price they go for is way to much for me to be okay with, and delivery time is also an effort.

 

As for WE, nothing really - Lack of trades was a minor niggle, but it was a great gun, shot well and cycled like a beast. Problem was I've realised now an AEG backup is a must-have, so the WE went in place of a G&P M4 V5.

 

As for settling on a GBBR M4; I figure the Bomber MRP should suit me just fine... It'll finally be in my hands tomorrow evening ;)

 

Generally, I've found thus;

 

KWA - Great out the box, reliable, solid gun. Can't fault it except the 3 piece upper, trades, and not as many things I can do to it.

WE - Again, great out the box. Overhops, but that's no issue with .4's. Only problems I had were again lack of markings and the unrealistic guts, while a silly thing, annoy me.

G&P WOC's are the one for me really; The LM4 and the WE just didn't feel the same as my G&P did, and I miss it. Now I can finally obtain the gun of my dreams from my favourite brand operating on my favourite system, that'll do me!

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About a year ago I switched over to an ORGA 400 x 6.23 under an 18" OP outer barrel; it performs really well and won't exceed 1J at various gases and BB weights (my site enforces a 1J limit). That extra two-tenths of a mm seemed small, but made a measurable difference. I was initially using a PDI 400 x 6.01.

 

I often run 152 on the 90+ degree days and I don't feel like the cycle is all that bad although I generally use semi auto since I don't carry many magazines (I have a full size M16A1 buffer and a PRIME steel bolt carrier, but stock WA springs). My idea of a good cycle rate is probably really slow compared to most - at the fastest, I think I've sent all 30 rounds out on semi auto in about 7 or 8 seconds? I've never really timed it, but I guess that is fairly slow compared to stock full auto AEGs.

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Yeah, I've heard a lot of that about the NPAS - Ideally I'd like to avoid it if at all possible.

 

Gas wise, I don't mind using Brut (what I use at the moment), but I'll make the switch to Propane eventually! I just refuse to buy it from anyone who isn't called Hank Hill.

 

So far then it's looking like increasing the thickness of the valve stem is the best option; Although I had good results clipping the spring in my LM4 - It took a little bit of fine tuning (clip/stretch/clip/clip/stretch) but it worked out well in the end.

 

A wide bore barrel is an option indeed, but the price they go for is way to much for me to be okay with, and delivery time is also an effort.

 

As for WE, nothing really - Lack of trades was a minor niggle, but it was a great gun, shot well and cycled like a beast. Problem was I've realised now an AEG backup is a must-have, so the WE went in place of a G&P M4 V5.

 

As for settling on a GBBR M4; I figure the Bomber MRP should suit me just fine... It'll finally be in my hands tomorrow evening ;)

 

Generally, I've found thus;

 

KWA - Great out the box, reliable, solid gun. Can't fault it except the 3 piece upper, trades, and not as many things I can do to it.

WE - Again, great out the box. Overhops, but that's no issue with .4's. Only problems I had were again lack of markings and the unrealistic guts, while a silly thing, annoy me.

G&P WOC's are the one for me really; The LM4 and the WE just didn't feel the same as my G&P did, and I miss it. Now I can finally obtain the gun of my dreams from my favourite brand operating on my favourite system, that'll do me!

 

Re: spring clipping, I tried the same thing, interesting that I did the whole clip/stretch thing too. Only problem is that surely the idea of clipping the spring is to make it weaker, but then when you stretch it you just negate that entirely? Eventually it got the point in my MP7 where the spring had been stretched so much that the valve wouldn't close and the gun just vented all the gas out the barrel on the first shot. (On a side note, really looking forward to more of Booey's teachings in the gas system thread, it would appear I still have much to learn!)

 

Do you have a link to Akira's mod? Sounds like something I should give a go. I'm also going to try heatshrink on the valve.

 

Lack of markings is a legit complaint, and to be fair I don't have a clue what the insides of an M4 look like, I thought the WE was a fairly good approximation (in open bolt form, obviously). Shows how much I know! :P

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  • 2 weeks later...

didn't read the entire post :P

 

What I did to 2 of my GBBRs, namely WE M4 ( with around 18" inner barrel ) and KJW KC02, both known to be way too hot for my region under certain circumstances

 

 

 

I got some of cable housing from my bike, particularly gear-shifting ones, stripped the guts ( some metal wire strands, teflon-like small tubing ) and keep the outer skin layer, cut out length of around 10mm and stuck into the loading nozzle

 

It holds itself sturdy enough ( in some guns ) to be not letting gas blow it out and effectively reduced forward-facing gas flow, not the best way to reduce muzzle energy but it's reversible and kind of "adjustable" ( I used un-stripped cable housing in my KC02, coz it's still too hot for just the skin )

 

the best part is, cable housing is virtually "free" if it's old and/or scrap pieces under certain length to be usable on bikes :unsure:

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