I would have thought it would be way easier to assign a cyclic rate to a given firearm in-game (for aesthetic playback purposes) and then cycle the single shot sound (maybe do it multi-channel so that multiple instances of the same shot can be heard playing entirely so it doesn't sound awful) at the same rate as the ROF of the gun when the player does a burst fire.

I've never automated the process of repeating a single gun sound over and over to simulate the firing of an automatic weapon, so that will be interesting, looks like it's something I will have to research, I'll see if it's possible with Audition, or audacity.