Its over on arfcom while some may not like that forum the thread itself is civil and very informative.
The content makes it worth mentioning here IMHO.
Gun writer David Fortier brings some relevant and eye opening data and commentary in there.

The thread is located in the alternate calibers section. I am posting the link cold.
http://www.ar15.com/forums/t_3_121/5...y_.html&page=1