black powder substitute

New to black powder, just got a 1847 Walker. The only thing I could find in stores near me now is Triple 7 FFG, which I have read is fine with this gun (vs FFFG). I'd like real black powder, that's tough at the moment. Triple 7 is hotter than black powder? How/when do I take this into account...

While looking for something else I came across an interesting article about firing undersized projectiles designed for cartridge arms out of a muzzleloader using sabots and/or paper patches. The idea was to test the performance of the projectiles at terminal velocities, but I'm sure muzzleloader...