I have a new expander for my dies that runs .002 larger than the old expander.  Never had a problem with bullet setback from 55 to 80 grain bullets.  Don't crimp my rounds either.

Neck tension is .004 with old and .002 with new.  Is there a preferred amount of tension for the .223 for an AR?

I use and recommend .003" of neck tension if you don't crimp.

Simply spin polish the expander ball to a smaller diameter. .2210" is the absolute smallest I would recommend, .2215" to .2220" is a better place to start.

Brass has spring in it, resisting change in dimensions. A .2220" expander ball should net a .2210" interior neck dimension, or if you prefer .003" of tension. I normally allow for .001" spring back. This amount would be unusual in brand new brass, maybe not enough after five + firings.  

Expander balls are cheap and easily modified by spin polishing them in an electric drill. 400 wet/dry followed by 600/1000 wet/dry paper makes for a superior mirror finish.

BTW - .002" is a good maximum tension for a bolt action. An absolute minimum requirement for a semi-auto.