Most modern star formulas call for KP (KClO4) but AP (NH4ClO4) is the closest I was able to obtain. However it seems converting to KP should be "easy" - at least in theory. I have calculated that 170g AP dissolved in half litre of boiling water combined with 108g KCl also dissolved in half litre of boiling water gives cca 200g KP dissolved in litre of boiling water. Solubility for KP in boiling water is 210,8g so it may stay dissolved. After lowering of temperature down to 0°C less than 8g KP would stay dissolved and the rest should crystallize out.
First question is if dissolving AP in boiling hot water is safe, and second one is if there is something important I overlooked?