Quote:
(5) Final Rule: Necessary for the cycle
of operations of the firearm.
The rule provides that ATF may also
consider whether the surface area that
allows the weapon to be fired from the
shoulder is created by a buffer tube,
receiver extension, component, or other
rearward attachment that is necessary
for the cycle of operations (i.e., to expel
a projectile by the action of an
explosive). This consideration is drawn
from the NPRM and the proposed
Worksheet 4999, which assessed two
points for ‘‘Extended AR-type Pistol
Buffer Tube,’’ ‘‘Inclusion of Folding
Adapter extending length of pull,’’ and
‘‘Use of ‘Spacers’ to extend length of
pull.’’ Id. at 30831. These extensions
provide additional material to the
firearm that is not required for the cycle
of operations and, therefore, can be an
indicator the firearm is designed, made,
and intended to be fired from the
shoulder. In contrast, material on a
firearm that extends the rear surface
area of the firearm toward the shooter
but is required for the cycle of
operations, such as an AR-type pistol
with a standard 6 to 6–1⁄2 inch buffer
tube, may be an indicator that the
firearm is not be designed, made, and
intended to be fired from the shoulder.
There is no such thing as "a standard 6 to 6–1⁄2 inch buffer tube" so this is more nonsense and error to be used to your determent. A 
