quote:

ACTION: Notice of proposed rulemaking; request for comment.

...

(page 27)

3. Split or modular frame or receiver
This second supplement would define “frame or receiver” to include “in the case
of a firearm with more than one part that provides housing or a structure designed to hold
or integrate one or more fire control or essential components . . . each such part, unless
one or more specific part(s) of the weapon is or has previously been determined by the
Director to be the frame or receiver.” It would further provide that “[i]n determining
whether specific part(s) of a weapon is the frame or receiver, which may include an
internal frame or chassis at least partially exposed to the exterior to allow identification,
the Director shall consider, at a minimum, whether the part may be identified legibly,
conspicuously, and in a manner not susceptible of being readily obliterated, altered, or
removed.” It would further make clear that “[f]rames or receivers of different weapons
that are combined to create a similar weapon each retain their respective classifications as
frames or receivers provided they retain their original design and configuration.”
This supplement to the general definition addresses one of the core problems of
the current definition of “firearm frame or receiver;” namely, that a majority of firearms
now use a split or modular design in which more than one part houses a different fire
control component and/or incorporates a striker instead of a hammer. It would make
clear that a firearm, including a silencer, can have more than one part that is the frame or
receiver that may need to be marked, assuming ATF has not already classified a specific
part or parts to be the frame or receiver. For this reason, manufacturers may wish to
submit samples to ATF for classification of one or more particular components as the
frame or receiver so that they need only mark a specific part or parts of a weapon, rather
than all qualifying parts (see Section II.H.10 of the preamble), or obtain a marking
variance (see Section II.H.6 of the preamble). However, this supplemental definition
would also make clear that ATF would not classify an internal frame or chassis as a
“frame or receiver” unless it is at least partially exposed to the exterior to allow
identification so that licensees accepting them into inventory can quickly record the
identifying markings, and law enforcement officers who recover the weapon can easily
see the identifying markings for tracing purposes.46