http://www.airsoftsociety.com/forums/f10/legacys-guide-building-high-speed-aeg-87504/
What I will say you must or highly suggest you should do:
bushings - not bearings - they will just collapse under stress unless you want to pay £30 ceramics and even then under gears bushings still best
AoE - sorbothane+neoprene mix
shs blue full metal rack piston - their other mixture pistons are not for high speed
(do not take the extreme pi$$ though with full metal rack - yes plastic/metal is wise but long term durability full metal rack is best imho)
deans + rewire with a MOSFET - think most people squeezing max speed/rof/response - whatever crap you wanna call it - many will be using this stuff anyway
o-ring nozzle but ensure it is exactly the same length or stay on original if unsure - a smidge too long and feed trouble, too short loss of fps/seal
(so if fitting an o-ring nozzle too short and lose fps you may as well stick with stock nozzle)
delay clip most likely will help
neodym motor - say shs torque is a good choice pulling stuff with a good increase over stock motors but there will come a point where speed becomes a problem and more work and more problems occur as you go on....
lame stock guns fire 13 to 15rps out of box aprox......
now you can get these near 20 by using 11.1v lipo but mosfet is wise consideration over time
or
powerful motor eg: shs torque neodym - but will get starved a bit on stock small tamiya - so deans
BUT do not combine neodym motor & 11.1v straight away - yes you will be getting high twenties but risk smashing f*ck out of box
Pre Engagement will take place as you get near 30rps on a stock gun with a stock m100 spring
I'll end repeating myself over and over again......
I would suggest - sticking on stock gears tbh - why coz you wanna learn to crawl/walk before you try to run/sprint
You can still hit a decent rof, your motor won't struggle and need a stronger one straight away
You fit a mosfet/rewire/deans etc.... now you can run 11.1v if seeking more speed
Look - think/decide just how fast you wanna go but most on here stick to twenty's as we have learnt:
Twenty's is plenty & it will last and nearly all mags - even crappy cheap high caps will feed fine
When you try to run 30+ lots of trouble and increased wear & failure tends to take place
Also good players do not need to overkill and hose people down - yes response n stuff is great
but it is the player's awareness & response not the gun's rof that usually wins the game