Preventing people under age 21 from buying guns will not prevent people under 21 from shooting guns. Our best friend's teenage son is a competitive marksman, despite the fact that he isn't even old enough to purchase a gun.
Preventing people under 21 implements check-and-balance that may prevent impulse purchase for the intent of immediate harm.
Hunters only. Rifles only. There is no need for anything more than that. Age doesn't matter in how guns are used. The goal in using guns is what effects how guns are used. Hunters have a valid reason and thus should be allowed to buy hunting guns. For self defense, it doesn't matter becuase the opponent can also have guns.
At the age of 18, All males must sign up for Selective Service. That means you are required by law to join the military if the government tells you to serve. Upheld, this means we can trust young men to go fight wars for their country before they can even individually own a firearm. Such a statement is ludicrous.
Eighteen is OK with me.
Twenty-one is OK with me.
Thirty is OK with me.
Sixty-five is OK with me.
Pick ONE age then make it apply to buying guns, signing contracts, joining the military, drinking alcohol, having casual sex, getting married and paying taxes.
It should be ALL OR NOTHING rather than this confusing array of rights/ages.
No no no we should leave the legal age to stay as it is at 18 rather than change everything to a higher age as I have read it will just infantilize younger adults and also because we are actually now adults at age 18 anyway as are bodies stop growing and developing and because we can do a lot of all things already like even adopt in many countries, vote, smoke, get married, get a job and also many more other things too. Also because 18 is the most popular age for adulthood and to do many of the things in society and in almost all countries.