RE: Hunting: Oil or No Oil?
About the only "no oil recommended" scenario I can think of is bitterly cold weather. When hunting is sub zero conditions with a bolt action rifle, I like to disassemble the bolt and spray the internals with Gun Scrubber (or Break Part Cleaner). After it warms up, you need to re-apply light oil.
The AR-15's need a certain amount of lube in the bolt carrier assembly to work. It is my understanding that as a result of our conflicts in Afganistan and Iraq, they are now recommending light grease for certain lubrication points that were previously lubed with the military Break Free - particularly the bolt carrier assembly internals and disconnector hook.
A lot of gunsmiths, including me, have gone to using the new synthetic oils. They do just about everything well . . .