G&G GR25 upgrade advice

[Sitting Duck]

I have serious doubts if your M125 spring is anything like what it should be

you should be hitting 410+ fps most likely 425fps or more with longer tbb

the variations & losses are down to seals at hop/nozzle/bucking sealing 101%

it is blowing if the nozzle doesn't seal 101%

this is why you was getting all sorts of results and got 345 then swap this n that

the hop/barrel was reassembled badly perhaps and so got 287/245 like Lozart & others are saying

I'm just also wondering is that spring anything like a m125 coz even @ 345fps on a good day you are way out

even if volume is out a bit (not a hell of a lot though not high enough volume for 0.30's)

you should still be hitting 400+ fps - no honestly it is way out imho

If 345fps was your best and all was looking good that spring is a m105 tops imho

I know this is additional crap but your spring sounds iffy as well to me

Is there any way you can get the spring tested or fit another that you know is deffo m125

that is if you are aiming for 425fps dmr ???

if you are trying just for 345fps regular aeg then ignore this post and concentrate on the hop/bucking area

but that m125 spring you say is in there is way out

need to get back to 345fps so reassemble hop again and fit the unit to gun carefully

the alignment of box tilting back from overtightening the stock tube etc... is a right pain to watch out for

basically if not careful the front of box can tip up and then nozzle scrapes at top of hop unit and crap seal

The M4's AEG's have a number of bastid qwerks and issues and can really do your head in

on top of the hop issue of blowing and a good drop in fps

Soz to chime in but that m125 spring is also looking suspect to me if the best you got is 345fps so far

 

[Samurai]

A few years ago I serviced an AK where I couldn't find the reason for a loss of 100fps for many tries. Everything looked perfect.

It turned out that it was the piston O ring (and cylinder and piston head combo). Testing them manually it was perfect airseal. With a finger on the cylinder head, I couldn't push the piston in. It was shooting 300 fps. Then I switched to an O ring that had very little resistance when testing manually. The piston was just slowed down a little. With that it shot the required 400 fps. When it was shooting full speed, the O ring squeezed too much between the piston head and cylinder wall and slowed down the piston. The one that felt too small on the manual test didn't expand that much on full speed, thus it created the perfect airseal. It was one of the more unusual cases.

 

[Jay91]

My gr25 had a sudden drop of about 70 fps on a game day, stripped it down and turns out the nozzle had an a leak. I used Teflon tape around the o ring as a quick fix and a test to ensure this was the cause. Got to be worth a try hth

 

[Azman1978]

Hmm. Fed up with it now. Have bitten the bullet and ordered an a&k v2.5 gearbox (elongated) for a good price and a prowin hop unit. Bit of tinkering and see if that fixes the issue. T least i will have more air to mive heavier bbs. 

 

[Hangtight]

Beware the Prowin. Often the cause of more problems than it ever solves.

 

[Azman1978]

Not an official prowin. Seen the state of some of those and gone for that style but different make. Right. Anyone know if the a&k lower reciever accepts the g&g upper? Thanks. Thinking about getting one to save shaving the innerds out of the g&g for correct fit. 

 

[Samurai]

I don't think so. Both are companies that make their own stuff their own way.

 

[Azman1978]

Okay will order a full upper and lower. Saves me chopping and means i can come up with something funky with the gr body. Right so had another play as the gr gearbox and setup was misfeeding. Turns out a priblem with the tappet plate so replaced with a spare i had. No misfeeding and now getting a consistent 369 to 372 fps. Happy with that variance. Must just mean the spring is crap. What spring would people recommend as a true m140 spring. Looking for a consistent 430 to 450 fps. 

 

[Azman1978]

Afternoon guys. Right. Its working again.  Cinsistant fps of circa 420. However... can someone tell me where the nozzle should sit after firing. Forwards or fully back? At the moment it seems to fit fully back but my head tells me it should be forwards and in the bucking??? If so how do i correct this? Cheers. 

 

[Sitting Duck]

What juice/volts are you running it on - 7.4v or 11.1v

you will get a tiny bit of over spin with SHS HT motor as it is a balanced more than a ultra torque

So it will be a bit quicker than the original motor - even a Blue Powerful or Orange Ifrit 25k

you may get a bit of overspin or rather nozzle retraction

the nozzle starts to retract just before the first teeth on piston/sector engage

so the nozzle will start retracting before any real tension from spring helps to stop the drivechain

if using 11.1v then you will get more overspin

However - you don't want the nozzle sealing on the bucking lips anyway

if you think about it if the nozzle has sealed tightly against the bucking in storage

well over time in storage those bucking lips might lose high efficiency sealing at higher 425fps

Quite normal for nozzle to retracted say 50% - if you run on 11.1v then just fire a few shots on a 7.4v to park it

 

[Azman1978]

Thanks for that. Running a 7.4 lipo. 3200mah. Can i retard the sector gear a touch to move the tappet nub a bit further away? Or would that not have any effect?  The nozzle is retracted all the way back so there is no movement so a little too much for my liking. 

Cheers

Aaron

 

[Sitting Duck]

if you look at pic...

by the time the sector meshes and begins to slow down from the spring tension as piston is drawn back

The tappet plate is approach full retraction...

I mean this has a delay clip and it is quite a large clip

I like the circular brass type that can be fitted either way and I fit it later

But even without any clip - the tappet is at 50/60% before the piston starts to retract

To get the gun to stop asap with less retraction you are probably looking at Active Breaking Mosfet

Or

Ensuring Cut Off Lever is brand new, trigger contacts not too tight-possible flaring of the contacts

So that the COL pops the trolley asap and that trolley is not gripped tightly by contacts so returns asap breaking circuit

(worn COL's and tight contacts can cause delay in breaking circuit & a bit more overspin)

TBH - just go with it, think of it as a bit of pre-cocking or chambering assistance if tappet is retracted a bit

fire gun on a low juice 7.4v 15c @ say 7v or something to help "park" the gun better for storage if ya really worried

 

[jeklund77]

Hi.
I´ve read this thread since I bought a G&G GR25 a while ago...

This is the recommendeation from a Swedish store thats sell and upgrades weapon.

I will leave it in swedish, but just translate it with google to see what they recommened for a 150-160 spring.

G&G GR25 Sniper (Recommendation for 150-160 spring)

Grejer man måste göra också/tänka på:   
Behålla dessa original (för att främst slippa matningsproblem, otät nozzle till gummi)
Hopup-Hus, Nozzle, Cylinderhuvud
BYT kullager till bussningar. Även om det är 8 eller 9 mm kullager. Vill ej ha ras på kullagren.
Shimsa dreven noggrant

Limma på original-cylinderhuvudets gummi en extra gummidämpning (så kallad sorbopad)
Utan detta så håller inte gearbox på Version 2, utan kommer spricka. Sedan med 160 trim så SKA alla bössor ha extra dämpning på cylinderhuvud.
http://www.rodastjarnan.com/39919

Med sorbopad + vanliga gummit på cylinderhuvud så får man kolla AoE på pistongen.
Så den kuggar i rätt. (Tänk på att 160 fjäder pressar fram pistongen något)
I värsta fall får man dremla ner tand nummer två kanske 1-2mm.

Parts for customer

http://www.rodastjarnan.com/airsoft/shs-staltandspistong-14-1/2-staltander-34403

http://www.rodastjarnan.com/airsoft/ultimate-pistonghuvud-aluminium-25505

http://www.rodastjarnan.com/airsoft/shs-super-high-torque-100:300-gen-iii-37698

http://www.rodastjarnan.com/airsoft/shs-high-torque-motor-lang-axel-29245

Cylinder av Stål med port/ingen port som passar piplängd och fjäderstyrka . 

G&G SR25 har 520mm! lång innerpipa. och originalcylinder är mässing.

(Innerpipan bör vara mellan 300mm till 430mm inte kortare, och inte längre!. Längre = boreup och boreup ställer till problem för nozzle (nästan alla boreup cylinderhuvuden har större nozzle-pip=original passar inte på den)
och hitta boreup-cylinder, pistong huvud, cylinderhuvud som passar ihop med samma boreup mått. 

Stålcylinder utan port så. Gärna SHS.
https://beta.rodastjarnan.com/airsoft/shs-cylinder-typ-a-35539

hopupgummi http://www.rodastjarnan.com/39956

h-spacer.. alla är slut utom konkav airsoft pro.

https://beta.rodastjarnan.com/airsoft/airsoftpro-konkav-spacer-hop-up-24272

shims http://www.rodastjarnan.com/17950

Mosfet Gate NANOHARD eller liknande.  Titan. Dessa klarar den mycket höga Ampere-belastningen och spikar som blir.

ASCU riskerar brinna upp. ASTER klarar mindre amp än titan. men vet inte hur mycket mindre. så tills dess så kan ja bara rekommendera Nanohard och Titan.

Keep:

hopuphus, nozzle."

Ha en fortsatt trevlig dag, mvh David