I just shot qualification this week. All the M4s in class were taken out of the armory and shot without adding any lube to any parts. 200+ rounds, zero malfunctions. Clean them with CLP, remove all carbon, wipe them down until there is not a trace of lubricant and turn them in back into the armory for the next time.
Down range, all I use is CLP, Otis to be precise. Works fine for me.