I just noticed that the Plasma caster does not show plasma bolts in third person view, but does when fired in first person.
This has to be a bug right?
This is what it looks like.
http://www.youtube.com/watch?v=Sbtqn1aIrw0

jay, same bug here - ive mod it with the faster-fire-rate mod - after this my lovly plasma caster was broken =/ now it shoots only straight up.... and wont deal any damage...

Something like that can happen if the node is misaligned (I'm not sure this is what's going on for you... but I was modding a gun and the very thing happened that it would only shoot up, and I believe it was the Y and Z axis were reversed).