I was 15 when I got my first shotgun. I had unfettered access to a .22
before that.
I was just looking at Maryland's gun laws including the most recent
changes. The focus of the changes seem to be on assault type "military"
looking long guns and restrictions on magazine capacities.
There still is no minimum age requirement to purchase and own a long gun
however and no permits, proof of training or anything is required.
Seems nuts to me in this day and age. The way I read it a 7 year old
can buy a shotgun or a .22.
A buyer must be 18 to purchase a long gun in Maryland.