State to state is tricky expecially when the states do not talk to each other.
When I am out of state in Michigan at my 2nd home, it is considered my domain and I am allowed to have my guns in the house. But, since I am a full time resident of IL, Michigan will not give me any time of carry license and will not honor my Chicago Firearms permit.
I may transfer my permanent residence to MI at some point, but then that causes problems in IL.
Very difficult with state to state.