10-3.7 Smokeless propellants intended for personal use in quantities not exceeding 20 lb (9.1 kg) may be stored in original containers in residences. Quantities exceeding 20 lb (9.1 kg), but not exceeding 50 lb (22.7 kg), may be stored in residences if kept in a wooden box or cabinet having walls of at least 1-in. (25.4-mm) nominal thickness.
Nowe, the big question is ... who the hell is going to inspect your house for how much powder you have stored? (It is also notable that certain areas will further restrict the amount of powder you have on-hand, if you are dumb enough to ask.)