.44-40 has a much larger base diameter than .44 Magnum/Special/Russian. So-called "5 in 1" blanks have been made for the movie industry that fit .45 Colt, .38-40, and .44-40 guns, as these three cases share the same base diameter. I suppose you might hypothetically be able to form .44-40 cases from .45 Colt, but I don't think it would be worth the effort.