I'm currently working on importing my real bullet cracks and distant combat sounds into the game.
Here are a few of my sounds added on top of a firefight to get a general idea as to what it may sound like:
It does not sound perfect as there is no reference point in the game for the cracks, they are just played stereo.
Some sounds are 'singular' meaning they can be played when one event happens (one crack, one whizz). Others will be harder to get in game as they are like 3 or 4 seconds long, and they may not make it in at all.
In almost all the firefights I've seen the crack and snap of bullets really adds to the intensity. I really wish I am able to find some way to increase the number of snaps and cracks (maybe increase the distance in which they are played) within the game as they are heard very rarely.