Welcome!
I haven't studied this in a while, but I recall the legal limit (Federal) is 25 pounds before you're required to use a powder magazine. And, there may be a licensing requirement (
application link). One of the links (below) implies a 50 pound exemption.
I don't shoot daily, but it takes me a -long- time to run through a pound of powder. Unless you're feeding a cannon, you shouldn't need anywhere near 25 lbs.
http://www.atf.gov/explarson/newslet...2001/page3.htm
http://a257.g.akamaitech.net/7/257/2...7cfr55.218.pdf
http://www.du.edu/~jcalvert/phys/bang.htm