Low FPS

[Misery]

ok so had my 2nd hand army armanent combat master delivered and seems to be suffering low fps like 100fps on .2s tried 3 diffrent mags and 2 diff tins of gas to rule out those mag or gas issues.Im leaning towards it being a nozzle issue as do get a bit of gas on the hand more than i would expect to be having anyway what do u guys think and what would u recomend to try before replacing parts?

 

[witchcraft58a]

I'm not a 1911 aficionado, but could it be light striking?  maybe worth taking apart, checking, cleaning and lubing the hammer assembly???

 

[Misery]

will give it a tear down in a bit and clean and lube everything,the sliding movement of the nozzle does feel a bit gritty and not as smooth return as id think there should be on that part but never having a gbbp before im out of my element checking up vids on youtube lol and wanting to hear peeps opinions on here

 

[witchcraft58a]

will give it a tear down in a bit and clean and lube everything,the sliding movement of the nozzle does feel a bit gritty and not as smooth return as id think there should be on that part but never having a gbbp before im out of my element checking up vids on youtube lol and wanting to hear peeps opinions on here

I kind of swear by WD40 Dry PTFE spray, its awesome stuff for airsoft use, has the benefit of not holding grit and gunking up internals.  Worth considering!

 

[Adolf Hamster]

so there are a couple of places you could be getting gas leaks.

the easiest to check is the hop-nozzle, if you pull the mag and very gently draw the slide back the nozzle should "stick" in the hop for a bit (although not to the point where you can lock the slide all the way back and it still sticks) aftermarket hop rubbers like the maple leaf autobot/decepticon have a little metal c-clip around one end to give a bit more pressure when sticking to the nozzle which can work a treat (although there is such a thing as too tight)

the second 2 aren't so easy.

first is the piston head which depends on the manufacturer, some use o-rings others use shaped pads and sometimes it's a mini piston head similar to an aeg, this could be worn. if the gun's spend a lot of time firing heavy ammo on high pressure gas there could also be a bulge in the nozzle cylinder which could mess things up as well. iirc (read: citation needed) the combat master is cloned tm internals so shouldn't be too hard to find a suitable replacement.

second is the mag-nozzle interface, this is a tricky one to really measure as it's not possible to really observe too well with the gun dissassembled. one thing to check is that the mag catch isn't worn as the mag sitting slightly lower down than normal means that gap will be giving a leak. if holding the magazine up into the gun cures the gas venting then this might be your problem. there are aftermarket gas routers by the likes of 9-ball although which exact version you want to use i'm not sure.

this is assuming the hammer spring isn't too weak as has been mentioned, and there's no dirt/grit blocking the system that would give a light strike. the other possibility is the float valve has a weak spring to it, closing too fast.

however given the thing is spewing gas i'd check the seals first and see what that does.

 

[Misery]

right checked nozzle that seems to "stick" the way u describe,what rubber would u recomend?

right cool to know its cloned tm and parts shouldnt be hard to find

check mag same issue regardless of holding all 3  mag in so definatly aint the interface of those

how do i go about checking for light strike?

will give evrything a once over

 

[Adolf Hamster]

right checked nozzle that seems to "stick" the way u describe,what rubber would u recomend?

sticking is good, should mean it's not leaking too bad there.

if you're wanting to blast some heavier ammo then the ml autobot/decepticon is my go-to for pistols with the vsr type bucking.

right cool to know its cloned tm and parts shouldnt be hard to find

i'm pretty sure it is, but there might be some proprietary stuff mixed in.

check mag same issue regardless of holding all 3  mag in so definatly aint the interface of those

hmm, unless all 3 mags are short then sounds like that's not the issue.

if it's still chucking out a lot of gas from the slide rather than the barrel i'm still thinking it's a leak somewhere around the nozzle, maybe the piston head is worn/loose.

or maybe a problem with the float valve.

tbh my gbb knowledge isn't massive so hopefully others might be able to chime in with more specific suggestions.

 

[Alimcd]

EDIT - BBU = Blow back unit

My suspicion echoes what Mr Hamster has said. 
 

I had a similar issue recently and it was the bolt that held the shaft inside of the bbu had loosened. It’s relatively easy to get to, you’ll need the slide off.

Remove the guide rod and barrel assembly. Loosen off the bolt at the rear of the slide and top bolt if there is one. The Bbu will either drop out of the slide at this point or you’ll have to gently push at the nozzle to get it out. 
 

Dont lose your nozzle spring when the BBU drops out! 
 

Pull and lift the nozzle out of the BBU housing and you should be able to have a gander at the piston/o ring assembly. Check the seal when reassembling and give it some silicone 

While you’ve got the nozzle out, it’s worth testing that the floor valve is moving freely. You can gently push the valve through the nozzle with a small Allen key or similar. It should spring back when pushed and should spring an Allen key across a desk...

Ali 

View attachment 69394

View attachment 69395

 

[Misery]

having delved more into it im suspecting the previous owner has worked on this found a broken mag release under the packaging,but also when looking at the piston assembly there seems to be a snapped screw going through the piston

View attachment 69396

is it me  or does that look to be missing an oring seal?

View attachment 69397

 

[Misery]

ok so looking at it i may just be better cutting my losses and ordering a new bbu to save trying to drill out that screw and rethread etc .so im assuming it would be the bbu and rocket valve thatid be replacing? minus  nozzle and piston head/piston head rubber they seem ok@Adolf Hamster @Alimcd

 

[Alimcd]

Just before you do,

Not all BBU’s are the same size/shape. I’ve struggled to get WE/KJ/elite to fit with certain slides etc and had to do a lot of filing etc.

I’d go down the repair route first. Hi-capa parts are a minefield and you can easily end up spending more on the replacement parts than the entire bloody pistol. (See my Novristch SSP1 thread as a prime example!) If you end up with a new BBU (25-30) and it needs a different nozzle due to tolerances (10-20) and the new nozzle needs a stiffer nozzle spring (5) 

It does look like there’s a ridge for an o ring. If you can get a seal there, I suspect the low FPS issue will be solved. 

EDIT- 

If you do want to replace it, Maybe try a TM unit as a first step?

http://www.eliteshootingcentre.co.uk/Gas Guns/Gas Pistol Parts/Items/TM slide stop.htm

 

[Misery]

i can get oem jw3 bbu from bespoke speaking with them just now about it

yeah wouldnt the missing screw head in the pic above that holds the rocket valve i think its called be blowing the seal aswell causing the issue?

yeah theres a fine ridge on it id reckon i could find a seal to fit that online

looking at 11.99 for the bbu and 1.99 for the rocket valve from bespoke

https://www.bespokeairsoft.co.uk/army-custom-5-1-4-3-jw3-baba-yaga-hi-capa-series-part-rocket-valve-r501-a-43?___SID=U

https://www.bespokeairsoft.co.uk/army-custom-5-1-4-3-hi-capa-series-part-blow-back-unit-r501-a-040

 

[Alimcd]

That’s way more reasonable than I was expecting for a BBU. 
 

The rocket valve assembly is all in the loading nozzle. As long as it closes when pressed in, it’s unlikely to be the cause of the issue.

Might be worth double checking with bespoke that the BBU assembly comes complete with the piston head. I’d be surprised if it didn’t but lots of daft things happen in Airsoft 

EDIT - Just followed your link for the BBU. It doesn’t look like it comes with the piston head. I’d ask them for a complete BBU + piston head. 

 

[Misery]

yeah he said in email they do the complete unit will get one ordered tonight i did send him that pic with the missing screw head so he knows exactly what parts im needing  rather than my crap describing haha

 

[Alimcd]

yeah he said in email they do the complete unit will get one ordered tonight i did send him that pic with the missing screw head so he knows exactly what parts im needing  rather than my crap describing haha

Awesome, I hope that’s problem solved. 

 

[Misery]

haha fingers crossed but knowing my luck another issue will; arise when i fix that one haha

 

[Adolf Hamster]

is it me  or does that look to be missing an oring seal?

View attachment 69397

nope that is the seal. the concept is the shape of it mushrooms out a bit when the gas pressure hits it sealing it up against the walls, although they do seem to be somewhat sensitive and easily worn.

it should have a very light fit to the nozzle going the whole way down, if the nozzle is bulged it might seem a nice fit at the end but not once it's all the way in.

you can get aftermarket styles that look almost like a miniature aeg piston head with a seperate o-ring.

having delved more into it im suspecting the previous owner has worked on this found a broken mag release under the packaging,but also when looking at the piston assembly there seems to be a snapped screw going through the piston

View attachment 69396

maybe a grub screw or a pin? can't really tell from the pic. in theory anything behind the piston head *shouldn't* matter for air seal so unless it's loose/wobbling then might not be an issue.

as @Alimcd sayd if you're replacing the bbu might as well change the nozzle as well, just in case it's scored/bulged/had the rocket valve spring snipped.

 

[Misery]

right having replaced the bbu piston head rubber and full nozzle assembly also fitted the autobot rubber im now into the 100fps consistently im attributing that to the hop rubber rather than the bbu itself,ok sothat rules out the compression side of things,so light striking you say how do i solve that issue? @Adolf Hamster @Alimcd

 

[Adolf Hamster]

Hmm.

Nozzle include a new float valve? Because that would have been my next suspect.

Light strikes could be a few things, mag position (forward/back rather than up/down as i mentioned before) for example i had to space the front of the magwell in the dragonuv because of that issue although less likely on a pistol.

Could also be the knocker is damaged, especialy cheap pot metal and a high round count where it mushrooms from repeated strikes.

Or the hammer spring is weak/the hammer is binding (might be the knocker binding too) and not falling with full authority. This would be compounded with say using a higher pressure gas such as black gas in warm weather.

Unfortunately this is pushing to the edge of my knowledge with gbb, normally i'll keep a pistol stock aside from the hop/barrel/piston head and the rest i just keep clean, lubricated and free to move as they should.

 

[Alimcd]

I’d be tempted to put a smudge of silicone grease around the hop rubber inside of the hop unit to prevent any potential leaks. Less is more on the grease.

Could be the gas routers not quite contacting the nozzle as Hamster mentioned earlier. I’ve got a couple of Novristch ones spare you’re welcome to if you want to test that?

Ali