Armox 500T is a special type of armor steel possessing superior mechanical properties suitable for use in vehicles and buildings need for first priority protection. Since these products are large-scale, a welding groove needs to be created before joining which can be done by milling operations. This study aims to address this point by questioning the impact of clean environments, namely, dry, minimum quantity lubrication (MQL), and LN2-based cryogenic cooling on the machining performance measures during milling. The novelty of this paper is the investigation of the effects of different cutting environments on the milling performance of Armox 500T armor steel. The results from this study showed that cryogenic medium has an impressive impact on controlling the temperatures at tool-chip interface which directly reduces flank wear development. In addition, cryogenic and MQL-assisted machining is much better than dry environment in achieving improved surface properties, chip shape, and energy consumptions. Cryogenic cooling seems as the best option for hard milling pursued by MQL and dry environments, respectively, from the sustainability and machinability point of view.