For a new production AR style rifle the difference between 223 and 5.56 is very
similar to buying 12 large eggs versus buying a dozen large eggs.

I use Accurate Arms 2230 powder, a mid-range powder charge for 50 gr HP bullets, and
shoot that load in 5 different rifles accurately without a problem. I use mixed brass
and don't sort headstamps. I make sure to separate range brass (military vs
commercial) to ream military primer pockets to remove the crimp.

I won't bore you with details about cleaning, tumbling, case length, and trimming
brass.


EDIT: A chronograph is the only thing that can tell the difference between a 3100 fps
or 2900 fps bullet. Neither a target or prairie dog knows the difference. A prairie
dog does know the difference between 223 and a 25-06 -- there is less to pickup if
you use a 25-06.


Makes me want to run right out and get a Mini-14.
--

Guns don't cause problems. The behavior
of certain gun owners causes problems.