Originally Posted by m4a1mustang

Well, you don't until you try.

I'd just go to cheaperthandirt.com for now and sort the 5.56 target ammo by price. Read reviews and order a few boxes of a few different brands that get good feedback and give it a shot.

Also keep in mind the weight of your bullets and the twist of your barrel... I believe some of the more aggressive twists don't like the heavier bullets, but I'm no expert on rifles. You'd have to ask Darren.