[simohayha]

guys,i have a question regarding gbb fps after mods.
when i first got the gun (hi capa 4.3 marui) the fps is around 310-ish using guarder black gas (i think its green gas/propane inside).
but after i mod the gun and install all the parts, i only got 290-300 fps.
i expect to have a higher than stock fps.....anyone know why this happens? or used to experience the same problem?
my parts are as follow (the one's i think effect performance):
-airsoft surgeon metal slide
-PDI 6.01 inner barrel for 4.3
-shooters design pom cylinder set/nozzle
-nine ball dyna piston head with replacement spring for the floating valve (harder spring)

the slide movement is smooth,used 1000 grid sandpaper to smoothen all the rails.im sure the mags is not defective.and gas consumption is okay (38 shots per 4.3 mags).
thanks