On BP it's not so much the amount but how you store it. The storage requirement is what discourages retailers. If you are storing BP incorrectly, you should heed the advice about no insurance.
We have tight wad skeet shooters who buy powder through the club when it orders targets, and they routinely load their cars with, and take to their homes, an illegal amount of powder and primers.
For any one who wants to research this (I don't care enough to), the info is hard to find because the local ordinances usually regulate it by incorporating by reference a universal fire code - so the exact specifications may not be found locally.
Some reloading manuals have an insert with the transportation and storage requirements.
