Interesting about the Brooklyn thing.
I live on Long Island myself, and one of the things I have to consider is the 'constructive possession' problem.
I have a black powder revolver, but I have not got a pistol permit yet.
This is perfectly legal, because in NY (state, not city) you are allowed to own black powder handguns as long as you don't own the materials needed to fire them.
If you want to shoot your pistol, you have to get a pistol permit and add the black powder pistol onto it. Once you've done that, you're allowed to own the powder, caps, and ball.
Now, although I do intend to get a pistol permit, I am not doing so just yet.
I don't own any powder, ball, or caps at the moment, but when I buy supplies for my cannon, I'm going to have to be careful!
From what I gather, I'm safe as long as I don't own ALL THREE items needed to fire my cap & ball revolver.
I can own fuse, as revolvers don't use fuses, and I don't need caps to fire cannon.
If I own fuse and powder, but no .44 ball or caps, I'm ok.
For instance, if I bought a cannon that was lanyard fired (with a cap) and was .44 caliber, I would not be able to buy the supplies necessary to fire it, because doing so would also mean that I had the necessary materials to fire my revolver too!