9.5.3 Distribution of estate firearms. A decedent’s registered NFA firearms may be conveyed taxexempt
to lawful heirs. These distributions are not treated as voluntary “transfers” under the NFA.
Rather, they are considered to be involuntary “transfers by operation of law.” Under this concept, ATF
will honor State court decisions relative to the ownership and right to possess NFA firearms. So, when
State courts authorize the distribution of estate firearms to decedents’ lawful heirs, ATF will approve the
distribution and registration to the heirs if the transactions are otherwise lawful. A lawful heir is anyone
named in the decedent’s will or, in the absence of a will, anyone entitled to inherit under the laws of the
State in which the decedent last resided.

170 18 U.S.C. 922(a)(4); 27 CFR 478.28
62
9.5.3.1 Distributions to heirs. Although these distributions are not treated as “transfers” for
purposes of the NFA, Form 5 must be filed by an executor or administrator to register a firearm
to a lawful heir and the form must be approved by ATF prior to distribution to the heir. The
form should be filed as soon as possible. However, ATF will allow a reasonable time to arrange
for the transfer. This generally should be done before probate is closed. When a firearm is being
transferred to an individual heir, his or her fingerprints on FBI Forms FD-258 must accompany
the transfer application. The application will be denied if the heir’s receipt or possession of the
firearm would violate Federal, State, or local law. The law enforcement certification on the form
need not be completed. The form should also be accompanied by documentation showing the
executor’s or administrator’s authority to distribute the firearm as well as the heir’s entitlement
to the firearm. Distributions to heirs should not be made until Forms 5 are approved. Executors
and administrators are not required to have estate firearms registered to them prior to distribution
to lawful heirs.

Quoted:
If you want to make it easy, have pre-filled form5s in the safe ready to mail and a will spelling out where each NFA item will go

Quoted:


This is my plan.  As each stamp comes back, the a form 5 will be filled out and placed with my will.