Help my new spring won't sit straight, in my G2 gearbox,

[Joyfull69]

As you can see in the pictures, the spring will pop up or down, sadly I didn't realize this when I first put the gun back together, it only cronoed at around 150fps, the spring is meant to put out 350fps so I'm hoping this is the issue, as the gun was working fine before hand

[E21A]

Is there a screw that holds on the buffer tube or anything like that? 

[Joyfull69]

To be honest mate, I'm new with internals, so I could be wrong but is this what you mean?? 

[E21A]

What’s the gun? 

 

There a thread in the spring guide there, guessing ( like the stock) screws on to the back of the gun. If so, that screw will hold the spring guide straight. 

 

What im trying to say is it’s very unlikely that the spring actually looks like it does it the photo, once the gun is fully assembled 

[Joyfull69]

I'm a twat ?? have just put the lower receiver back on and as you said it looks fine, I guess I'm just looking for issues now, as I thought that might be the reason the fps has dropped so rapidly since I put the new spring in, the gun is a Spartan Delta SX18 M4, any ideas on why the fps could have dropped would be amazing, thanks for your help mate 

[E21A]

Guessing this is your first time opening a gearbox? If so, it’s likely you’ve put something back wrong or forgotten to do something. 

 

Is the spring the only only thing you’ve changed? 

[Joyfull69]

Yeah the spring is the only thing I have touched, it's a quick change system too so I didn't even have to open the gearbox to do it, thanks for taking the time to help me out with this mate 

 

[Nick G]

might be worth checking that the hop unit is sitting against the gearbox properly. It sounds like you have got an air leak. Is the hop set correctly ? having no hop on can cause a low fps, is the nozzle ok ? no signs of damage from removing the box ?

[E21A]

8 minutes ago, Joyfull69 said:

Yeah the spring is the only thing I have touched, it's a quick change system too so I didn't even have to open the gearbox to do it, thanks for taking the time to help me out with this mate 

 

 

Swapped the old one back? 

[ak2m4]

very rarely will changing a spring cause 150fps drop, however there's always that chance the something in the gearbox is misaligned or very slim chance cracked the piston head.  You may have to open it up.

- What was the fps before the new spring was added?
- As E2 mentioned have you tried putting the original spring back?

[Joyfull69]

I can't see any signs of damage, it was pretty easy to get to the box, the hop up looks good and fits right to the nozzle.

 

The fps was around 230 as I accidentally cut to much of my old spring off.

I just did a couple test shots as I put it back together, didn't bother cronoing as I could have caught the bbs they were going so slow.

 

I have just noticed that  the Piston (maybe) is not going back where it belongs every time, picture will be below as a picture says 1000 words.

[ak2m4]

Don't worry about the piston not going back to the same spot each time that's normal, what you can do as a test to make sure the piston is going all the way back each time is fire it so it's in an uncompressed state and then with a long screwdriver or rod through the nozzle you should be able to push the piston all the way back.  What brand of spring did you fit?

[Joyfull69]

The spring was a ASG m100, and the Piston seems fine, pushes all the way and then the spring will push it back fine 

[ak2m4]

hmmmmm, when you dry fire with the gearbox out of the hop chamber can you feel a decent amount of air being pushed out of the nozzle?  Only thing I can think off is when you insert a mag something is pushing the hop chamber off alignment, creating a gap that air is escaping

[Joyfull69]

Yeah feels like 300+fps of air ( compared the air flow to my Tommy gun ), so your thought would be that the hop up is the issue, 

 

[ak2m4]

it's all about eliminating the various components. 

 

Did you take the hop chamber apart and examine the bucking for damage?  That's the next thing to do, good opportunity to give everything a clean as well.

 

you could try shooting it without the lower receiver, holding the mag, barrel etc tight against the gearbox, it's a bit tricky and not the best test, may help

[Joyfull69]

To be honest mate, I don't have any idea how to take this hop up apart, just looks like solid metal to me.

 

Will try that test tomorrow

Forgot to attach 

I managed to take the hop up unit apart and the bucking looks good to me, no noticable wear on it at all 

[Joyfull69]

Just going to buy a new gearbox, thanks for the help lads 

 

[ProPain87]

Did you disassemble the whole gearbox or just change the spring via the quick change spring guide?

 

*edit*

just read the thread properly, answers my question ??‍♂️

[E21A]

8 hours ago, Joyfull69 said:

Just going to buy a new gearbox, thanks for the help lads 

 

 

Ermmm, why? ?

[ak2m4]

nah buddy don't buy a new one, where about's in the UK are you?  maybe someone is close by to take a look at it.  If you're near me in Kent happy for you to drop it off for me to take a look

[Joyfull69]

Sadly in in Southampton, and I was looking at getting a mosfet fitted, and found a completly upgraded gearbox, so I'm probably just going to buy that and then I can tinker and learn from the gearbox I already have,