Re: AR's and chrome lined barrels.
I personally went without chrome, on purpose, in my new AR and I am happy with my decision. Too many stories around about the chrome lining spalling off and ruining the gun's accuracy for me to be comfortable. I was going for maximum accuracy itn the AR I was putting together.
That said though as Woolyworm says, if you're fond of doing a bunch of high speed mag. dumps or you don't clean your guns after each use, definitely go with the chrome. It will protect the bore and make it much easier to clean.
I have several rifles that are over 100 y.o., that have been well cared for, and they are still as mirror bright as the day they came out of the factory. Their bores aren't chrome lined and they still shoot with laser-like accuracy. I see no reason why my AR range-gun can't also perform in the same manner with proper care.
Fear is a reaction..........Courage is a decision