This has nothing to do with cheating.

In the normal damage model the automatic weapons do NOT take someone out with one round unless it is in the head. If it is a leg, arm or torso hit an automatic weapon will require several hits to bring someone down. I routinely see three or four blood squirts from someone at point blank range and they do not go down.

The realistic model is better in that regard and is, well, more realistic. Even if there are times when you need more than one round there too, not nearly as many though.