Replies

The International Fire Code (IFC) is widely adopted (my conservative county in a conservative state has adopted it).

Chapter 33 relates to explosives and fireworks.
http://www2.rigov.org/pdf/inspections/2003InternationCodes/2003InternationalFireCode.pdf

It exempts the following from its rules:
The possession, storage, and use of not more than 1
pound (0.454 kg) of commercially manufactured
sporting black powder, 20 pounds (9 kg) of smokeless
powder and 10,000 small arms primers for hand loading
of small arms ammunition for personal consumption.

and

The possession, storage and use of small arms ammunition
when packaged in accordance with DOTn
packaging requirements.

(But that is not to say that anything more than this is prohibited or regulated.)

Important definitions:

SMALL ARMS AMMUNITION. A shotgun, rifle or pistol
cartridge and any cartridge for propellant-actuated devices.
This definition does not include military ammunition containing
bursting charges or incendiary, trace, spotting or pyrotechnic
projectiles.
SMALL ARMS PRIMERS. Small percussion-sensitive explosive
charges, encased in a cap, used to ignite propellant
powder.
SMOKELESS PROPELLANTS. Solid propellants, commonly
referred to as smokeless powders, used in small arms
ammunition, cannons, rockets, propellant-actuated devices
and similar articles.

Section 3306 relates to Small Arms Ammunition

3306.4.1 Black powder and smokeless propellants. Propellants
for personal use in quantities not exceeding 20
pounds (9 kg) of black powder or 20 pounds (9 kg) of
smokeless powder shall be stored in original containers in
occupancies limited to Group R-3. Smokeless powder in
quantities exceeding 20 pounds (9 kg) but not exceeding 50
pounds (23 kg) kept in a wooden box or cabinet having walls
of at least 1 inch (25 mm) nominal thickness shall be
allowed to be stored in occupancies limited to Group R-3.
Quantities exceeding these amounts shall not be stored in
any Group R occupancy.

3306.4.2 Small arms primers. No more than 10,000 small
arms primers shall be stored in occupancies limited to
Group R-3.

(Group R-3 represents a normal house, as opposed to a hotel or apartment.)