Provided is a method and system for making powdered Fe16N2. The method can include sealing iron powder and a fixed amount of ammonia (NH3) gas within a pressure vessel. The pressure of the fixed amount of ammonia gas in the pressure vessel can be elevated so that Fe16N2 can be formed from the iron powder. Use of a pressure vessel and a fixed amount of ammonia gas can provide economic and environmental benefits such as higher conversion rates of iron powder into Fe16N2, reduced ammonia gas use, and reclamation of used ammonia gas.