I love the 223 for varmints. It is fun and relatively cheap to shoot.
if you need a bunch of decent brass for a good price check www.rvow.com
-- if you dont need so much, go with winchester or lapua.
anywho -- i love it for PD's and groundhogs -- i have dropped several ghogs in their tracks past 400yds with 50 vmax, It will get you to 500 on varmints as long as you can get it there--heavy bullets like dave shoots will get you there with a little more poop left--but for that (with factory guns)you need to get a savage with a 9 twist barrel--most others are 12 twist (like mine) and can only go up to about 60gns.