you can buy a gun at the age of 18. you have to be 21 to carry a concealed gun or permit. Anyone can carry a "rifle" or a gun with a 16 inch barrel anywhere any time as long as it is visible.Unless its a courthouse/schoolzone restricted area like a club. All semi-auto guns are legal.Upon purchase of a gun they will do a federal background check that usually take 30 minutes. I have about 160 guns lol