ICS MP5 + Guarder SP150KIT - low Fps issue

[crazyguy]

Hey there,

i have put inside a ics mp5a5
Guarder FTK torque up kit sp150
with a guarder reinforced shell (looks pretty strong! )
and a new guarder anti heat switch
systema super torque motor (not magnum, the older version!)
intellect 1200mah 9.6V!

its shoots pretty smooth,
i dont think there is any air leaks.. because i greased the cylinder pretty well with marui original silicon grease.

it looks like it shoots 300-330FPS

i i have another gearbox that shoots 410 FPS and i can see the big diffrence,

anyway, could it be cause of the stock barrel?

when i shoot blank i feel the strongest air stream i have ever felt but stil.. loe fps..

any one have an idea?
Thanks!
Guy.

[Skruface]

There's no way the FPS should be that low, even with a stock barrel. You need to look for air leakage.

Check the o-rings around the piston head and cylinder head, and see if the o-ring is still inside the nozzle. Check the hopup rubber and make sure it's sealing against the barrel and not leaking air.

Are you testing for FPS with the hopup on or off?

If you can't find any air leaks, I'd check the spring in another gun - if the FPS is also low, it's the spring. After confirming there's no air leaks or a weak spring, I'd then start looking at the barrel.

[crazyguy]

well the hopup bucking is brand new acctually..

i used it couple minutes ago with another original ics gearbox with a 120 spring and it works perfectly..
so if the ics gearbox runs great it means there is no air leaks in the hopup right?..

and i changed the boreup kit with a normal set and an original ics airnozzle witch is a 1mm larger then Guarder or any other marui air nozzle, i think it works better but still, not 150 M\s how it should..
maybe 120 M\s..

and again about air leaking problems and such, i greased it a few times with sevral grease types,
the guarder cylinder head is no way have leaks in it! its insane how strong it goes into the cylinder it self, and it seems that there is no air leaking at all..

i was thinking about ordering a new systema 6.04 229mm barrel and a new hopup chamber..
but i need to be sure its really the problem.

here is some pic of this set:
http://www.shakel.co.il/guy/sp150.zip

and i tried installing the 120 spring in the sp150 gearbox and still doesnt act like a 120 spring!
it seems to be only a air leak after all..

[joaz]

looks like way too much grease on the piston head..

[CDN_Stalker]

Wow, a 500fps MP5! That's gotta be a bruiser, literally.

[crazyguy]

really? can over greased piston head cause this?

it looks like the bore up cylinder should be without grease at all but i didnt checked it out, acctually i sold the bore up kit it self..

i have now a standart cylinder with a 6 hole piston head.

[joaz]

Yes. The O-Ring is supposed to expand through the vented piston head.
Too much grease can prevent this.