Target Sports has 5.56 for 40ish cents per round.
https://www.targetsportsusa.com/wolf-gold-556-mm-nato-m193-ammo-55-grain-fmj-wm193-p-110223.aspx
https://www.targetsportsusa.com/wolf-gold-556-mm-nato-m193-ammo-55-grain-fmj-wm193-p-110223.aspx