Palmetto has the Federal 7.62x51 for $9.99/box of 20. Shipping is not free, but that's the best price I've seen on brass/boxer in a few years.
http://palmettostatearmory.com/index.php/ar-10/7-62-x-51mm-nato-149gr-fmj-m80-20rds-xm80cl.html
http://palmettostatearmory.com/index.php/ar-10/7-62-x-51mm-nato-149gr-fmj-m80-20rds-xm80cl.html