Another thing - while screaming 'MAKE IT BASSIER AND DEEPER' is all fun and games for the iconic bolter rifle (yes, it's fielded like a rifle, although as we know by our reality standards it's more of an rpg.) remember that there are weapons with higher weapon calibre, so those weapons kind of need to get first pick on the bassiest and deepsiest of sounds. Take for example, the heavy bolter... which fires even bigger rounds, even faster. ..and then there is the autocannon!
It should sound like a bass cannon mixed with the sound of a missile launcher and some kind of grenade?
My opinion here is - it should sound like it's closest analogs in real life - PAW 20 and XM25. The destructive power should be at least similar as well (watch and estimate).
It should sound like the most cliche of machine gun noises that served as the ultimate filler soundboard in any given action flick... or put it another way; what relic dubbed as bolters in Dawn of War!
I'm hoping for a little creativity for holy weapons... Seriously,something closer to the "heavy" sound of big caliber machine guns, than fast firing assault rifles, would be great..like this: View: http://www.youtube.com/watch?v=tgXWJEZzFHE
dull launch & explosive impact on target....better question is what kind of targeting system standard bolter will have...??? I see it like this: TAU (Target Allocation Utility) from bolter to helmet's visor supported with ITI (Independent Target Infictor) from astartes helmet to bolter, physical and neural symbiosis of weapon and his genetic owner...