Well if you have a sound clip of multiple bullets fired (like a burst) then AH will try to play that entire clip every time a single bullet is fired. AH tries to play a sound for every round, I think.
If you're getting a burst, a pause, and a burst, it's probably that you've got dead air in the wav file.
The wav file probably has a gap after the burst, and AH is playing that pause before it re-starts the sound file.
Try trimming the tail end of the clip, take out any pauses, and/or (just my opinion) try to get it down to a single bullet if you can, so that when you're firing away it doesn't sound like there's 2 dozen guns all firing at the same time instead of 2.*
* = I have heard some that didn't run into any problems on steady-fire loop sounds, but they didn't sound right in short bursts.
