The best thing to do for tournaments is to have some where you're expected to have them so if you don't then you can't complain about bringing a knife to a gunfight, and some tournaments where guns are banned outside of super bad ones like civil war muskets. For normal ranked battles if we are using non guns then don't accept challenges from guns without stipulations in place prohibiting things like one shots and allowing you to claim that they're missing on occasions where it's not obvious they wouldn't miss, meaning that even if your character has normal human reactions and speed, if they're a decent distance away and at least making an effort to dodge then the dodges can succeed, guns hitting once they have no options to dodge, requiring the gun user to play smart and get them in a trap in order to take full advantage of their gun.
We could all do a non ranked realistic gun battle to practice gun fighting tactics if we wanted to.
LeeRoy