Also, How does the Light Weight Profile differ, if it does, from a government profile barrel?
Take a look at the CALIBER button on the 223 on the main page. It has some pics and you will get some idea. a "gov't" profile, I guess, is the M$. It is cut heavily in various places. You can see it very well in the pictures.
The best firearm for self defense? Any loaded one will do.