7.4v lipo 25c or 30c
13:1 will get you about 26 - 27 on VERY THICK 16 awg wire, mosfet deans etc....
12:1 will get you near 30's.......
additional boosts depend on using very fast torquey motors like Big Dragon M160
SHS torque is not quite as fast but close and easier to get hold of
other crazy motors like G&P Satan I can't comment on
not even got a Lonex motor
Speed motors get very very hot pushing past m100 springs - so don't think of a shs high speed
some torque motors are not much faster than stock ferrite motors but designed for pulling crazy mofo springs m150+
even frankentorque motors are not ultra quick - just ultra strong
bushings are a must in high rof but will be slower than bearings - 5 to 8%
ceramics offer speed & strength but jeez not cheap and still mofo builds need bushings under spur gear
the choice of neodym motor can make a big difference
but it can only unleash its full power if all the wiring homework is done - often a dremmel to squeeze in thick wire
the box will just die quicker - much quicker unless you get EVERYTHING as close to perfection as possible (not easy)
plus after all that crap - you can still find it feeds crap coz it needs a stiffer tappet spring to load bb's quicker etc....
it is a MASSIVE learning curve and no I am no expert - just broke LOADS taking the pi$$
if you wanna go nutz - do it in stages is my advice
read:
http://www.airsoftsociety.com/forums/f10/legacys-guide-building-high-speed-aeg-87504/
go easy and take your time
try to learn to walk before you try and run
later builds will be much better than your first few attempts - well mine were $hite
overcoming problems - learning from mistakes etc....
airsoft teching is no way as easy as them youtube vids look and still I think there is a sprinkle of luck required
(or loads of luck in mine & many others builds)