ive tested its ROF with a few batteries using audacity
FPS was 416~421 with hop up all the way off
Sanyo 8.4v 600mah nicd gave me 15rps = 900 rpm
Morepower 12.8v LifePO4 1600mah = 19rps = 1140rpm
G&P 9.6v large 3300 mah = 19.6rps = 1176rpm
Firefox 9.6v crane stock type battery 2000mah = 19rps = 1140rpm
Firefox 11.1v 1600mah Lipo(Voltage confirmed 12.55v fully charged) = 25rps = 1500 rpm
lipo won hands down, but this thing can eat an entire hicap in 12 seconds provided that you can wind it fast enough.
it also has an interesting hop up rubber, I should write a review on it soon.