RE: Hunting: Oil or No Oil?
Yes, the action should be oiled. A LIGHT film of gun oil on the bolt. Avoid too much oil, especially in dusty climes. Whilst hunting, you want the inside of the barrel unoiled. You DONT want oil in your chamber or on your sear.
While hunting (assuming cold weather) I always allow the rifle to come up to room temp before removing it from the gun case, to avoid sweating. I clean the action and the exterior of the rifle, then apply a light coat of decent gun oil, I prefer Eezox.
An AR-15 has a rotary bolt, which performs the same task as a bolt actions bolt does. I have never hunted with an AR-15. I did serve in the USMC. We were told to apply a light fil of oil to the bolt carrier group. Of course, I didnt care for the military's choice of gun oil, Break Free (CLP) sucks green tomatoes.
Side Note -Degreasing your bolt action rifle's action and bolt, then working the action a hundred or so times is a good way to increase the smoothness of your action.