No, unfortunately, the only firearms an 18 yr old can purchase from a federal dealer is a long gun. Stripped lowers can only be purchased at 21 yrs old+
Not sure if they sell lowers. If the lower would be made into a rifle, it could be purchased by an 18 yr old. I'd call them though and they could explain. It's a fine line when buying a lower since it could be built as an AR pistol. They'll get you the right answer.
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