is a m120 spring can break a normal gearbox?

[crazyguy]

hey there, a little background on me,

im from israel and as you probebly know there isnt many places here you can ask for help.

any way, i have a ICS Mp5a5 ver 3.5 (upgraded by airsoft elite)
with intellect 9.6v 1200mah.

after about 20000 shoots my gearbox shell broke and i bought a TM one from UNCOMPANY since they didnt have an ICS one..

the TM shell is not reinforced (i think)

anyway, in the begining i had many problems with it.. i made some modifications to the switch bar so it can fit the TM shell right and i needed to modify the tappet plate as well...
and i bought a Hurricane 120S kit..

i noticed some few problems.. my fps was dropped to 150-200 (instead of 330 before)
the first thing i noticed was that the new airnozzle i got with the hurricane kit is about 1mm shorter then the ICS one but when i put the ICS one it doesnt take bullets to the gun so i modify it too... now the gun shoots but i dont know how strong (i dont have a chrono now..)

when i disammble the hopup it shoots to 13-15 meters and falls (is that normal?)

when i installed the 120 spring, in the start the wires were pretty hot and after a few shoots the gears was stock or the motor didnt have any more power to stretch the spring, then i worked on the shimming hard, and since then the gear didnt stuck but the motor sometimes dont have enougth power to pull the spring... my ROF is pretty low... i turend it back to my m100 spring that i had with my ICS (after all it has being threw 20000 shoots..) i think its pretty weak...

anyway do you know if the m120 can break my gearbox shell? (i have a aluminium piston)

i have a HFC m190 gun also and it seems to have more power then my ICS one..

any suggestions for the normal power i used to have?..

and im not sure the TM shell fits good with the hopup chamber.
another small maybe abig problem, after shooting a single shoot? the airnozzle lefts behing, it means that bullets can get into the barrel freely(the hopup stops them ofcourse)