First of all,
http://www.huxley-universe.de/img/151106_02.jpg
Looks like actual projectiles to me. Whether or not they have collision involved, with the damage implemented that way, of if they are just 'actors' is up in the air. But those looks like projectiles do they not? Coming from two rifle-looking weapons...
Also, not sure about the assault rifle in UT2k4, but I am positive the minigun has tracers, at least. And there is travel time.