That's actually where democracy came from. When guns came along, it became extremely cheap and easy to turn every random peasant into a soldier. This meant that you essentially always had to have the will of the people on your side.
I guess hypothetically it doesn't take long to teach someone how to use a gun, but based on my interactions with people who refuse to touch a gun or want to destroy any current legal firearm ownership legislation - teaching them to be proficient with a firearm will be an entirely different ballgame.