Buncha good replies. Just thought some internet accessible material was warranted:
Here's several examples of 8th AF gun attacks (air to air and air to ground) w/o tracers - some seem to show some sporadic/occasional tracers but that may be the 'end of belt' thing mentioned:
(Youtube link:https://www.youtube.com/watch?time_continue=139&v=nzTCJI863N4)
I suspect the engine and gun noises were added for entertainment effect like the music. I wasn't aware of sound recordings used in the planes then (or now, for that matter). In the mid forties that would require extra equipment/weight.
(I would be interested in knowing more if anyone knows of actual WWII gun film footage shot with sound on film technology.)