A novel high power (5-10 MW) crossed-field amplifier (RPCFA) based on the Recirculating Planar Magnetron concept invented at the University of Michigan has been designed and tested. Using computational modeling tools such as HFSS and MAGIC, a 3.0 GHz amplifier design has been modeled with 13.5 dB of gain (29 MW output). In simulation, the amplifier is zero-drive stable and exhibits greater than 50% electronic efficiency, not accounting for electron end loss; or 15% including end-loss. This RPCFA design was fabricated, constructed, and experimentally demonstrated, exhibiting amplification between 2.4 and 3.05 GHz, with peak powers up to 5-6 MW at peak gain of 8-10 dB. Maximum microwave output power is limited by RF breakdown in the slow-wave structure, which occurs between 3-6 MW. Amplifier gain exhibits improved reproducibility above 350 kW input microwave power. The RPCFA also demonstrated zero drive stability in experiments, up to 10 kA of injected current.