Standard 4-inch poured concrete flooring is really all that is required for an indoor range. Some range owners choose to finish the floor out with a gloss coating or paint. While this does look nice and adds a completed look to the room, just know that within a short time the floor will become scarred from low shots, especially downrange near the bullet trap.
For walls there are really three options. First is poured concrete walls; 8” for rifle rated ranges and 6” for pistol rated. Second is CMU or concrete block walls that are completely filled with grout or concrete. 12” blocks for rifle rated ranges an 8” blocks for pistol rated ranges. Walls should be 13’4” in height. This height allows the perfect amount of room to hang bar joist for baffle and target retriever connections and allows room for lighting and ventilation ducting. Of course, existing buildings being converted into ranges with higher or lower ceilings can be used with slight modifications made to accommodate for the space available. Third is to apply steel plating or panels over existing walls that may not be thick enough. This mostly applies to existing structures when a new wall with the above specifications cannot be constructed.