I just did some Googling and it seems that CUtlLinkedList overflow! (exhausted index range) is not limited to TF2, but is an error message you can get in any Source-based game. This thread seems to indicate that improperly referenced sprites quickly flood entity data, which would make it logical that quickly fired scattergun shots would make the game crash more quickly than individual pistol shots. Then the game would proceed to stop drawing any entities altogether because it's still trying to work on the tracers. My best guess is that someone at Valve rewrote something which calls for the tracer sprites and either made a typo or didn't reference the full sprite name.
Which brings up another question: If you have tracers enabled, do the tracers ever actually appear before you crash, or do you never see any tracers? If you don't see any tracers at all, I'd say that someone made a bit of a catastrophic typo and the game is desperately trying to draw tracers and it can't find them. This would also explain why pipes and rockets are fine.
N.B. I had to ask a friend what all of this means after I found that thread and he had very little time, so please don't have an aneurysm if I used any inappropriate jargon or if the way I worded things isn't strictly correct in programming terms. I am not a very good programmer and have no experience with game engines.