well most cartrige cases are brass but i have seen a lot the big cartriges from the A10 warthog plane that are steel (i live a few miles from there range and seen them out side there range on the ground )as melting brass it melts around 2300 f and if your doing this make sure you are were protective clothing i have seen this DO MAJOR damage to some ones body i have never melted cartriges but have melted hundreds of pounds of brass with my buddy makeing turn of the century motorcycles parts so every thing we have melted is thick brass witch is harder to melt i'm not sure of you furnace setup we use a reverbatory furnace with a stock becket oilburner with a gallon an hour tip it melts a pot of brass in about 45 min