It will happen with the guns. D.C. will pass some national gun-ban (probably AR-15 or something) and force confiscate. Red states will simply outright refuse and will fight back against federal enforcement that try to come in and do it (civilians will probably do the shooting, but the states will let them, they just simply can refuse to prosecute). That will be when all the red states secede or form a convention, lines will be drawn, civil war will be here.
It will happen with the guns. D.C. will pass some national gun-ban (probably AR-15 or something) and force confiscate. Red states will simply outright refuse and will fight back against federal enforcement that try to come in and do it (civilians will probably do the shooting, but the states will let them, they just simply can refuse to prosecute). That will be when all the red states secede or form a convention, lines will be drawn, civil war will be here.