Apparently the air in sporting goods store these days is so foul that it dulls the brain. I can't believe that there isn't some kind of shooting club, or range, or both within a short drive of any store that caters to shooting sports.
If there is such a club or range near by, what is wrong with the store owner arranging to build and store his powder at the range in a bunker or building that meets the storage regulations? He can arrange either to pick up the powder daily, or weekly, and deliver it to his customers in his parking lot out of his car, or have someone at the club deliver it daily or weekly for his customers.
Such an arrangement will meet all the concerns of Homeland Security, will cement ties between the gunshop and the gun club or range users, will provide a source of powder for both members, and new shooters who might be attracted to the range availability, as well as sending new customers to the gunstore not only to buy black powder, but also to buy everything else gun related. As to the cost of building the bunker, most gun club members would be happy to provide the labor to build it if it means the difference between having a local source of powder, or not.
These regulations are anti-gun, anti-hunting, and have little to do with national security. They are bad laws. Until they are repealed or change, however, we have to suffer them. IF WE DON'T WORK TOGETHER, we will lose! As our Founding Fathers proclaimed, "Either Hang together, or surely you will Hang separately! "
If the owner of the gunshop you frequent is not smart enough to figure out what to do, TELL HIM. Then talk to your gun club, or range owners, to work this out with him. Its not unusual for many ranges to have a powder magazine, because of the amount of powder they sell and use monthly. Why not help out the gunshop in town by "renting " him space in a magazine? Or build one for both parties to use? The " rent " can be allowing members to order powder at a discount from the gunshop owner. No, he doesn't make his usual profit, but he gets a bunch of customers( for other supplies) , and free sales reps telling other shooters where to find a great gunshop, no?