No. It's as simple as that.
No
Ammunition.
Rifle, Shotgun, Handgun, Artillery
Rifle or handgun?
You will have to specifiy if it is a handgun, rifle or shotgun.
18 for a shotgun/hunting rifle, and 21 for a handgun.
caliber
Caliber
The grooves in the barrel.
.22 Long Rifle bullets...
Under FEDERAL law, which applies in every state, you must be 21 to purchase ammo for a handgun. Ammo that may be used in a handgun or rifle may be purchased at 18 IF the seller knows that it will be used for a rifle.
I think large, heavy, expensive, custom made double barreled rifle. To the best of my knowledge, there was one handgun made in .600 Nitro Express, more as a curiousity than a usable handgun.