I notice that 5.56 is again getting an unrealistically bad rap. It's not as powerful as many other rounds, but some online epithets seem to suggest you can hide behind a sheet of paper and be safe.
As a reminder, I'd like to repost the following demonstrations from the fine folks at Box O' Truth:
There are certainly better rounds for long range and heavy targets (I like 8mm Mauser, myself), but don't dismiss a threat because he "only" has 5.56mm.
Oh, and off topic, but of interest: How .410 revolvers stink as defensive weapons.
- Michael Z. Williamson, SurvivalBlog Editor at Large