Abstract: Model rocketry powered by self-cast potassium nitrate/sugar (KNSB) propellant presents a unique and under-documented safety challenge. Unlike commercially certified APCP motors, KNSB propellant is mixed, cast, and cured by the amateur operator, introducing propellant chemistry, grain defect, and batch variability hazards absent from commercial motor use. This paper addresses four subsystem safety domains — Structure, Propulsion, Recovery, and Payload/Avionics — within the context of KNSB-propelled amateur rockets operating at motor Classes D–H (total impulse 2.5–160 N·s). Methods: A four-pillar safety framework is developed: (1) a seventeen-item Failure Mode and Effects Analysis (FMEA) per MIL-STD-1629A across all four subsystems, with particular emphasis on KNSB-specific propulsion failure modes; (2) a KNSB propellant safety protocol covering formulation, mixing, casting, curing, and storage; (3) a quantitative launch-site geometry model deriving minimum lateral safety perimeters from first-principles apogee and wind-drift equations calibrated for KNSB thrust profiles; and (4) a 46-point pre-launch readiness checklist with full FMEA traceability. Results: Grain cracking (RPN = 432) and motor retention failure (RPN = 504) are the two dominant hazards; both are reducible to RPN < 80 through targeted controls. The KNSB propulsion subsystem accounts for 51 % of the cumulative FMEA RPN across all seventeen items, confirming that propulsion is the primary safety driver in self-cast rocketry. Wind-corrected safety perimeters at the 9 m/s abort threshold exceed NAR tabulated minimums by 6–10× for KNSB Classes E–H. Conclusions: KNSB self-cast rocketry requires a safety framework that extends substantially beyond the commercial motor user’s protocol. The dominant risk pathway is not ignition or flight but propellant preparation: improper KNO₃/sugar ratio, moisture contamination, and grain void formation are the three highest-probability routes to a catastro