hi!
thanks for the idea, but the bad thing about brushes is that they need to have direct contact with the projectile which means that there's increased friction at that point. (not to mention that i'm using talcum powder which would more or less get between projectile and brushes and might at times cause problems)
also, the projectile takes up eddy currents from the electromagnetic field which result in very high spikes when the brushes get in contact with the projectile.
in the meantime i found some SIPMOS-FETs with switching speeds around 3ns at 24V.
never the less, thanks,
technosquirrel101