Its funny how the movie Eraser has permanently placed in the public mind that Gauss Rifles create tiny circles as they travel through the air.
Eraser? For me it was Quake 3 Arena - different gun, I know, but I liked it 
Funny you say that, because I was thinking more quake2 style particles rather than static texture per ring type deal or a little more.
Yes it's quite hard to get a decent feel for the effect till you see it and as long as the falloff speed of the rings are very short then it should be ok, just a bit bright in my opinion. But I think it would benefit from a center particle system. Try looking at
this not that I designed the graphics or anything

, I think it looks a bit more like a slug being launched, rather than a wave/beam type weapon.