The accuracy in these parts is MOLON. He has a tacked thread at the top of the ar discussions with links to all his major posts. You will learn a metric crap-ton about accuracy there.
Standard m4's are generally 1-3 moa. Every rifle will shoot better with a different ammo. mil-surplus is about 3 moa capable. Even out of a match gun, because of the bullets and variences of the powder charges, you will only get a 2-3" group (typically).
Dont expect to shoot this good your first time out with an ar. I have about 1k rounds of bench shooting under my belt now and its finally time to start changing ammo, I'm getting 2-5" groups at 100yds with brown bear and 5.56 (iron sights). These are 5 shot groups and i know some error is mine - im shooting irons. If you want to test the accuracy of the gun, get a 10x+ scope, an experienced shooter, and ammo the gun likes and do 3, 10-round groups. This will give you the machanical accuracy of the gun. You can assume that every round (with the given ammo) will fall inside that circle.