UDK collision system worst in engines in history?

Well while it probably it is capable of everything why is it so complicated to use? Or even function sometimes.
I am programming a ballista with Rigid bodies well KActor Spawnables as projectiles and you can register the hit but not the touch and the settings are cahotic, even on an archetype, any docouments On that? I better make my own collision system for UDK as the one is there already emmh… ehem…