In theory maybe, but you will blow coolant well before you reach 280deg. Been there done that many times. Lots of other ugly things will happen before this as well.
The pressure in the cap is supposed to be lower than the next weakest point in the system. A balance between the boil and blowing a hose, gasket, radiator seal, etc. Take an old poorly maintained car and put on a new cap, other things start to get leaky.