Edited on Tue Mar-01-11 11:42 AM by -..__...
It's a little murky; it is prohibited (by an FFL), to sell a shotgun with an attached pistol grip to anyone under 21... however, it is allowed to sell
a shotgun with both a stock and a pistol grip.
The way I'm reading it, is that as long as the pistol grip isn't attached at the time of sale... the transfer is legal.
If transferee later attaches the pistol grip, that is legal also (the provisions of quoted regulations and the GCA , only pertains to what an FFL can or can not do... not the guns owner)...
AGE RESTRICTION REMINDER
Licensees are reminded that certain commercially
produced “shotguns” do not fall within the
definition of shotgun under the GCA. Firearms
such as the Mossberg Model 500 Camper,
Persuader 500 and all other makes and models,
which come equipped with a pistol grip in place
of the butt stock, are not shotguns under the GCA.
Therefore, they cannot be sold or delivered by a
licensee to any person less than 21 years of age.
http://www.atf.gov/publications/newsletters/ffl/ffl-newsletter-1998-08.pdf
“Shotguns” with pistol grips attached
In the last ATF Newsletter (August 1998) an
article stated shotguns with pistol grips and no
shoulder stocks attached were restricted to
persons 21 years of age or older if being sold by a
Federal firearms licensee. This requirement is
specified in 27 CFR § 178.99(b) and 18 U.S.C.
922(b)(1) (www.atf.treas.gov/core/regulations/
27cfr178.html), which states that if the firearm to
be transferred is “other than a rifle or shotgun”
then the purchaser must be 21 years of age. The
definition of a shotgun under the GCA <18 U.S.C.[br />§ 921(a)(5)] is a weapon “intended to be fired
from the shoulder.” With the pistol grip in lieu of
the shoulder stock, this weapon is not designed to
be fired from the shoulder, and therefore is not a
shotgun.
Questions have been raised about those firearms
that are supplied with both a pistol grip and a
shoulder stock. If the firearm is sold with the
shoulder stock then the firearm is intended to be
fired from the shoulder and would be considered a
shotgun. The shoulder stock does not necessarily
have to be attached at the time. Persons 18 years
of age or older may purchase those firearms from
licensees.
Other questions raised pertain to entries made in
the licensee’s required records as to firearm
“type” if not shotgun. These entries may indicate
the firearm type simply as Title I.
http://www.atf.gov/publications/newsletters/ffl/ffl-newsletter-1999-02.pdf