http://www.youtube.com/watch?v=4EViRCdwo4s

There are two types of gunshot sounds for many weapons, one Normal sound, and one Distant sound for when NPCs shoot from further away. The transition from Normal to Distant is bugged however, as you can hear here.

What I think is supposed to happen is that as distance increases the Distant sound blends in while the Normal sound fades out, but what actually happens is that the Distant sound does not start playing until the Normal sound is completely silent.

This causes a gap at a certain distance where the gunfire is near silent, and then suddenly goes louder suddenly when you move further away from the shooter.

I hope Obsidian will have a look at this for the next patch.

speed of sound v. speed of bullet? or echoes? never noticed anything like that when I played.

It's the sound that comes from the gun when shot. Up close you can hear it fine. At 0:10-0:18 I'm further away and you can barely hear it. Then at 0:20-0:23 I'm even further away and the distant gunfire sound kicks in, and goes away again when I get closer.

Nope, that doesn't happen in my game. That's all I can tell you...sound card/driver related I'd assume.

I'll see if there's anything wrong with those then. I do have a decent sound card though (X-fi Xtreme Gamer) and my sound drivers are up to date.

I agree with the OP, distant gunfire is buggy. Often a distant battle sounds like it's going on right next to me. I've got the same sound card, too.

It is buggy, its not a driver issue. It has been attempted to fix multiple times by modders. Personally im using a sound replacement pack that fixes it.