M120 gearbox or M170?

[Bdot]

i have a m4, and i am wondering what gearbox i should get for it. Its between a M170 systema Magnum gearbox and a systema M120 torque up gearbox. If i was to get a M170 i would put a M120 spring in it so i am able to use it at places. also if i got the M170 and put a M120 spring i would change to a lower battery so it doesnt break. I was wondering if anyone knows if getting a M170 and putting a M120 spring in it or just getting the M120 gearbox which one would work better. because i know the M170 has better parts but would it work better or is it better just to get the one thats made for it. also do u think if i got the M170 itll have a lot of problems? thanks

[Azathoth]

A friend of mine bought a M170 gearbox w/ magnum mosfet. The price was the same as a M120 gearbox but without a mosfet and motor so for him a bargain. He swapped out the spring and is running 11.1 lipo.

He's got some problems with the box. shoots too fast with the lipo

His box came without a bearing spring guide (had this instead), and either torque or torque + gears (helical). All in all a good price but he ended replacing the spring guide recently.

My 120 box without motor that i brought from HK had standard flat gears (torque). Never had to replace anything other than the piston, and gears after 3 years and well over 300k rounds.

If you don't have friends/family oversea's buy the 170 box with the FET and motor and swap the spring.