Why? Becuase at 18 you're an adult legally speaking and as an adult you have all the rights that someone 25 30 50 or 100 hasgun control is a series of steps - if you can't pass a vetted BG check, you shouldn't own a gun. how is it you have more red tape prohibiting renting a fukking car before 25, something we're licensed to drive 9 years prior, but you can buy an automatic assault rifle at 18? these are common sense controls. additionally, if we can charge $6/gallon for gas, an essential part of life, why not make ammo $6/bullet, gun use is a hobby, make people pay for the luxury of using their gun via ammo
You don't have a "right" to drive or be able to rent a car ...you DO have a right to own a gun just like you have a right to vote, a right to not have your property taken by the govt, or to be made to be a witness against yourself or say what you want about the govt or any old subject with out the government censoring you ....
There's no such thing as prohibiting someone of their "right" to something thats clearly granted by constitutional law becuase they are an adult but in the opinion of some "not adult" enough ...