Originally Posted by L473ncy
M100 IIRC is supposed to be the same as a TM spring. M90 90%, M120 120% etc.
Although there are companies who have their own system. Best bet is to check out the spring chart somewhere on this forum (it's also been posted around on redwolf and Arnies IIRC).
SNK is right, M-ratings mean meters per second and %-ratings mean % of stock 280 FPS speeds.
Although some companies M-ratings differ from other companies, so it's sometimes kind of hand-wavy. That's where Illusion's spring chart comes in handy.