However back in the 70's after the Omnibus Crime Control Act shut us all down to a 5# limit on powder, Senate Bill 1096 was passed raising that limit to 50#.
AND
The law from that bill declares that all muzzle loading ordnance pre-dating 1999 is-not/are-not "firearms".
BUT
big brother being what he/it is, you may spend a lot of time and money defending that position after the siezing of your property and your own incarceration.
While DD is saying you likely will not want ot know the answer to your question, I am saying you likely will not like the consequence of shooting your ordnance on public lands.
However we had a board member who asked his local law enforcement office about shooting in his county (he was rural) and they sent a deputy out to observe, supervise and he otherwise got infected with our own peculiar kind of "disease".
GOW