I am assuming that when you talk about 62gr, your are referring to xm855 62gr?
Most bulk 62gr (Like mx855) ammo is lousy for accuracy in most AR's. If you are just doing some plinking, that's fine. If you are looking for real accuracy look for something like Hornady's 75 BTHP Match, Federal GMM with a 69gr SMK, or reload.
Even cheap 55gr Hornady FMJ-BT's can be loaded for better accuracy in a good rifle, in comparisons that I have done.