I fired two motors this past Saturday. One was an AP based motor and the other was a KNO3 based motor. Both motors were of approximately the same total impulse, but it wasn't really a fair comparison. The KNO3 motor used Xylitol for the fuel. I first heard about this sugar on Scott Fintels web site, and it was available at the local Whole Foods store. It has a low melting point and casts very nicely, the problem was that the grains took a long time to cure, weeks in fact. Anyhow, the propellant in the AP motor is fully characterized and the propellant in the KNO3 motor not so much. The side by side comparison is still interesting to watch though.