Finally got the OSA gold. Thanks for the advice! I got more progress in 3 days of casually playing HC TDM with the VMC, Grip, Suppressor, Rifled Barrel, and FMJ(because I'm going to hit cover even when burst-firing and I'd rather have it do a little bit of damage) than I have since I first got that Camo Challenge started.

Thanks everyone for the tips. Working on max-leveling the other ARs and getting them gold(KBAR is fully-prestiged and I still have a few camos left but I'm working on getting all ARs max-leveling before getting Gold).