I'm not sure how familiar you are with the nature of civil wars, but they usually end up splitting the military into two factions. Consider that one party in the US clearly wants to switch our government to a Socialist Democracy and the other clearly wants to retain the Federal Republic we started with, it isn't hard to imagine a split along those lines that would result in a major portion of the military joining the rebellion.
Once a state tries to secede by force, Congress would authorize the use of the military under the Posse Comitatus act and the President would order them in to restore order and enforce federal laws. Handguns and shotguns will only make you a target, and with all the registration laws, the Feds will know exactly where to go and who to ask for when they get there. Infrared displays will show them how many people are in the house, and if they are currently armed, and a single guided missile (not even a Tomahawk) will reduce the place to a pile of rubble without putting a single Fed at risk.
Or they could just starve the rebellion, since most farms are corporate owned, and wait for the cities to die off before rumbling in and declaring martial law. Or set off an EMP a mile overhead, instantly putting a city like... LA... into the 18th century.
Carry a gun for personal protection, but don't buy into the illusion that you are protecting yourself from tyrannical government unless you can start buying weapons of mass destruction, laser guided missiles, and fully armed gunships to level the playing field.