Left 4 Dead 2 accuracy - when can I stop shooting?

Solution 1:

I would recomend using hunting rifle, I've reached 95% accuracy at the end of a co-op campaign while using it once. But to answer your question: 1) Accuracy doesn't count kills, it counts hits. As long as you hit your targets you're doing well. And it doesn't matter who else is shooting the target. 2) From what I noticed (but it's actually hard to measure) bullets count as hits as long as they hit the hitbox and it doesn't matter if the target is already dead or not. Tank's hitbox disappear a second later than his actuall death. If you continue to shoot him, that's still going to count as hits. Common zombies' hitbox disappear a split second after their death.

P.S. L4D stats are often so bugged that I feel sorry for your trying to reach a certain value at accuracy...

Solution 2:

If you want to use an automatic rifle, I recommend you to use short bursts of two ore three shots. From my tries, this was the most accurate way to inflict as much damage as possible without missing.