If you go poking around your local government officials you are likely to get an ill-informed and incorrect answer. They are quite likely to say something stupid because they don't know, don't know where to find out, and don't want to get in trouble for telling you that you can store too much.
I did this. I asked. Believe it or not, I was told numerous times that I could not store any. None at all.
I believe that the National Rifle Assoc has successfully secured legislation that allows its members to keep up to 50 lbs of BP for use in powder-burning firearms. That allowance does not apply to rocketry or any use other than firearms. Some states allow less.
For your own protection, you should store any large quantity in a sand box. I built a box in the garage out of particle board with a plug in the bottom and a lid on the top that are removable. Motors that I store long-term I keep in there. I put motors into sealed plastic containers, stack them in the box, and pour sand all around and over the containers. The sand helps moderate the temperatures in summer and winter, would absorb lots of heat if anything burned around the outside of the box, and would also absorb lots of heat if any of the motors somehow ignited. When I want something out of storage, I pull the plug, drain the sand into a bucket, get what I want, and pour the sand back into the top. This may all be overkill but I feel better about storing a couple-hundred BP motors in my home.
