(c) In checked baggage.
A passenger may not transport or offer for transport in checked baggage or in baggage carried in an inaccessible cargo hold under §1562.23 of this chapter:
(1) Any loaded firearm(s).
(2) Any unloaded firearm(s) unless—
(i) The passenger declares to the aircraft operator, either orally or in writing, before checking the baggage, that the passenger has a firearm in his or her bag and that it is unloaded;
(ii) The firearm is unloaded;
(iii) The firearm is carried in a hard-sided container; and
(iv) The container in which it is carried is locked, and only the passenger retains the key or combination.
(3) Any unauthorized explosive or incendiary.
(d) Ammunition. This section does not prohibit the carriage of ammunition in checked baggage or in the same container as a firearm.
Title 49 CFR part 175 provides additional requirements governing carriage of ammunition on aircraft.