i have spc900 with 6mm lens. i tried 4,3mm also, but it gives distortion, so i want to buy industrial camera with C-Mount lens mount for example

http://www.globalspec.com/FeaturedProducts/Detail/Lumenera/Lu075_HighSpeed_USB_20_Industrial_Camera/26788/0

has anybody tried lens with C-mount? are better?
which camera to choose?

You should go for the FireflyMV , it does 120fps@320x240 and 60fps at vga res but is fast , low latency and really powerfull and hackable.
It’s probably way cheaper to than a industrial camera , you can get one of ebay for about 2-3$ bucks , but if your spc900 isn’t cutting it , the firefly should be more than enough.