I have a question about interstate sales. I Live in Northern indiana. I want to sell a gun to my friend in Greater Cleveland area. And he is going to sell me a different gun. I was not sure if its legal for us to do this inter-state. I would go to cleveland area and we would trade guns plus the difference in cash. Then I would transfer my gun back in my car. So my main question is this legal for me to transport a gun after a private sale, across the state.
-Nick

Also, if this is not legal, how could I do it legally.

A face to face transfer would not be legal.  If the firearms are rifles or shotguns, the easiest way to transfer them to each other would be through an Ohio dealer.  Ohio allows transfers of rifles and shotguns to residents of contiguous states. If the firearms are handguns, the transfers must be processed by a dealer in your respective home states.

Transport of a firearm would be legal as long as the firearm is unloaded and in a locked container or trunk of the vehicle.