I am not aware of a single State or Federal regulation that speaks to non-commercial storage of any HazMat material. In every case I'm aware of, so long as you may possess the thing, you may store the thing however and in whatever quantity you want.
Title 18, United States Code, Sec. 1102, Chapter 40. Importation, Manufacture, Distribution and Storage of Explosive Materials
§845.
Exceptions; Relief From Disabilities (a) Except in the case of subsection (l), (m), (n), or (o) of section 842 and subsections (d), (e), (f), (g), (h), and (i) of section 844 of this title,
this chapter shall not apply to: …, (4) small arms ammunition and components thereof; (5)
commercially manufactured black powder in quantities not to exceed fifty pounds, percussion caps, safety and pyrotechnic fuses, quills, quick and slow matches, and friction primers, intended to be used solely for sporting, recreational, or cultural purposes in antique firearms as defined in section 921(a)(16) of title 18 of the United States Code, or in antique devices as exempted from the term “destructive device” in section 921(a)(4) of title 18 of the United States Code;
So, as long as you're not storing more than 50 pounds of commercially manufactured black powder for sporting, recreational, or cultural purposes, you are not required to adhere to the storage requirements.
Go over 50 lbs. and you MIGHT be in violation at the Federal Level.
Title 27,
United States Code Code of Federal Regulations, Part 555—Commerce in Explosives
§555.26 Prohibited shipment, transportation, receipt, possession, or distribution of explosive materials. (a) General. No person, other than a licensee or permittee knowingly may transport, ship, cause to be transported, or receive any explosive materials: Provided, that the provisions of this paragraph (a)
do not apply to the lawful purchase by a nonlicensee or nonpermittee of commercially manufactured black powder in quantities not to exceed 50 pounds, if the black powder is intended to be used solely for sporting, recreational, or cultural purposes in antique firearms as defined in 18 U.S.C. 921(a)(16), or in antique devices as exempted from the term “destructive device” in 18 U.S.C. 921(a)(4).
SO..., the minute you buy black powder in person, you are "receiving" it, and the journey home, whether on foot or by some other means is "transport", so as long as it's under 50 pounds to be used in sporting, recreational, or cultural purposes, you're fine, OR if you order it online, then you are "causing it to be transported", and again as long as it's under 50 pounds to be used in sporting, recreational, or cultural purposes, you're fine
§555.41 General. (a) Licenses and permits issued prior to May 24, 2003.
(1) Each person intending to engage in business as an importer or manufacturer of, or a dealer in, explosive materials, including black powder, must, before commencing business, obtain the license required by this subpart for the business to be operated
. Each person who intends to acquire for use explosive materials from a licensee in a State other than the State in which he resides, or from a foreign country, or who intends to transport explosive materials in interstate or foreign commerce, must obtain a permit under this subpart
; except that it is not necessary to obtain a permit if the user intends to lawfully purchase: (i) Explosive materials from a licensee in a State contiguous to the user's State of residence and the user's State of residence has enacted legislation, currently in force, specifically authorizing a resident of that State to purchase explosive materials in a contiguous State;
or (ii) Commercially manufactured black powder in quantities not to exceed 50 pounds, intended to be used solely for sporting, recreational, or cultural purposes in antique firearms or in antique devices.
And this last citation above, shows that it's OK to get the black powder in another state, but AGAIN, as long as it's under 50 pounds to be used in sporting, recreational, or cultural purposes.
PLEASE NOTE all you DIY black powder makers, and/or users of the same, these exemptions do not apply when the black powder is not "commercially manufactured". Just FYI....,
LD