JG Sales has a smoking deal on some Federal 5.56.
420-round ammo can
62 grain XM855
$124.95 per can
The only catch is that you have to buy 4 cans to get that price. But you will not find a better price anywhere. Most places have it for $180 or more.
I just bought 4 cans, and even with shipping, its under 32 cents per round.
http://www.jgsales.com/5.56mm-federa...n.-p-5876.html