Actually i believe the CA law allows up to 5 lbs. but it is confusing and many BP shooters out there seem to have no problem buying in 25# lots???
CA Health and safety Code
12001. This part does not apply to any of the following:
(a) Any person engaged in the transportation of explosives
regulated by, and when subject to, the provisions of Division 14
(commencing with Section 31600) of the Vehicle Code.
(b) Small arms ammunition of .75 caliber or less when designated
as a division 1.4 explosive by the United States Department of
Transportation.
(c) Fireworks regulated under Part 2 (commencing with Section
12500) of this division, including, but not limited to, special
effects pyrotechnics regulated by the State Fire Marshal pursuant to
Section 12555.
(d) Any explosives while in the course of transportation via
railroad, aircraft, water, or highway when the explosives are in
actual movement and under the jurisdiction of and in conformity with
regulations adopted by the United States Department of
Transportation, United States Coast Guard, or the Federal Aviation
Agency. However, no explosives shall be sold, given away, or
delivered except as provided in Section 12120.
(e) Special fireworks classified by the United States Department
of Transportation as division 1.3 explosives when those special
fireworks are regulated under Part 2 (commencing with Section 12500)
of this division, when a permit has been issued pursuant to
regulations of the State Fire Marshal.
(f) (1) Black powder in quantities of 25 pounds or less in the
hands of a retailer having a permit issued under Article 2
(commencing with Section 6066) of Chapter 2 of Part 1 of Division 2
of the Revenue and Taxation Code and in quantities of five pounds or
less in the hands of all others and smokeless powder in quantities of
20 pounds or less used, possessed, stored, sold, or transported that
is exempted under, or authorized by, the Federal Organized Crime
Control Act of 1970 (Public Law 91-452) and applicable federal
regulations thereunder.
(2) All cities, counties, and special districts and county service
areas providing fire protection shall require retailers in
possession of black powder to notify fire authorities.
The referenced applicable Federal law:
Public Law 93-639 (1975) allows nonlicensees/nonpermittees to purchase commercially manufactured black powder, in quantities of 50 pounds or less, solely for sporting, recreational or cultural purposes for use in antique firearms or antique devices. A nonlicensee or nonpermittee purchasing black powder under the exemption need not be a resident of the State in which the dealer is located. Also, the categories of persons to whom the distribution of explosive materials is prohibited do not apply to black powder transactions made under the exemption.