Buying a gun from a dealer is controlled by Federal law- 18 for a rifle or shotgun, 21 for a handgun.
18
18 for rifle or shotgun, 21 for handguns. This is set by Federal law. 18 US code, section 922
Depends on what you are buying, where you are buying it and your age.
the proper size
You have to be 18 to buy a long gun and 21 to buy a hand gun.
Yes, anyone over the age of 18 can purchase any ammunition for any sort of long gun, but you must be 21 yrs of age or older for the purchase of handgun ammunition such as .40 .45 9mm .357 .44 etc
18
In California have to be 18 years or older to purchase a gun but any one can buy a hopper because it is not considered a weapon
In the US, 21 years old.
Yes
18
18.