Federal Lake City 55 grain FMJ Ball. This is the generic AR ammo. Bulk available almost anywhere today, stacks a Gander Mountain available all over from 120 round plastic boxes to 1,000 round Cardboard. See Targetsportsusa.com or just about any online or local dealer. The experts (Example Pat Sweeney of the AR-15 books) tell me 62 grain military (also available from Federal) is not as good on ballistic effects, but may be more accurate at long range. For hunting get a good hollow point and keep the game in the varmint category. Despite the reports of SMALL deer taken with heavier .223 bullets I tend to think of .243 and up for deer. Check your local/state laws as well.
Geoff
Who needs to take his Sport to the range, but this is the hottest week of the year in NE Florida.