In his/her other posts, s/he asks about shotgun shells and how to buy .22 ammo,
says s/he isn't yet 17, wants to buy a pistol on turning 18, then says s/he is 18 (all posts were made on the same day),
says s/he doesn't want a rifle, only a pistol, then in this post says s/he has a rifle.
I think this is a LE troll trying to find people advocating illegal actions.
Good thing we don't do that here.
***** my original post *****
You have to be 21 to buy handgun ammo.
Since you're buying it for a rifle, it's legal.
(No, the laws don't make any sense.)
If it's WM policy not to sell to adults under 21, that's their problem, but it's not the law & they shouldn't be blaming their bad policy on the law.
Go to a dealer or sports store where people know the laws.
Maybe take along a picture of you with your rifle?
Or make friends with someone & trade things of value - do him/her some service & s/he buys you the ammo.
Or get a gift from a friend or relative.
How about going to wherever/whoever you bought the rifle from?