ics m4 upper gearbox upgrade

[seanycozzie24v]

im going to refurb my upper gearbox by regreasing it, new spring etc. im looking to fit a m120 spring. my upper gearbox is already slightly upgraded with the ics pom reinforced piston and a ported piston head. still has the standard cylinder head/cylinder and spring guide afaik. realistically what fps should i get out of it with the upgrades and the M120 spring? thanks in advance

 

[RR01]

The last AEG I put an M120 in was shooting about 380fps, far to high for most sites.

 

[seanycozzie24v]

my m4 is shooting at a very low fps at the moment. 268fps i think the springs on its way out. all the seals are fine. maybe 360fps with the new spring?

 

[seanycozzie24v]

also my outdoor site has a fps limit of 365fps

 

[seanycozzie24v]

and whats the best grease to use for the piston rails, seals etc