At about 12:50 EDT, the propeller of a Nanchang CJ-6 struck the pilot/owner after the engine started while he was rotating the propeller by hand. The pilot was preparing the engine for start. The pilot reported that the radial engine on his airplane was susceptible to hydraulic lock if not started within 40 minutes from shutdown. The propeller needed to be pulled through in order to start. After shutting off all the valves and switches, the pilot went to rotate the propeller. He stated that the propeller had not even rotated 90 degrees when the engine fired and started. The pilot said he forgot to turn off the magneto switch.