49 CFR § 173.171 - Smokeless powder for small arms.
Smokeless powder for small arms which has been classed in Division 1.3 or Division 1.4 may be re classed in Division 4.1, for domestic transportation by motor vehicle, rail car, vessel, or cargo-only aircraft, subject to the following conditions:
(b) The total quantity of smokeless powder may not exceed 45.4 kg (100 pounds) net mass in:
(1) One transport vehicle or cargo-only aircraft; or
(c) Only combination packagings with inner packagings not exceeding 3.6 kg (8 pounds) net mass are authorized. Inner packagings must be arranged and protected so as to prevent simultaneous ignition of the contents. The complete package must be of the same type which has been examined as required in § 173.56 of this part.
(d) Inside packages that have been examined and approved by the Associate Administrator may be packaged in UN 4G fiberboard boxes meeting the Packing Group I performance level, provided all inside containers are packed to prevent shifting and the net weight of smokeless powder in any one box does not exceed 7.3 kg (16 pounds).