It could be done with a rotating magazine, I suppose. But I don't think the .45 ACP won't give you much more performance out of a long barrel. The .45 Colt, .44 Mag, and even .357 can be cranked up and almost turn into completely new cartridges when fired from a levergun. Some .44 Mag loads are on par with full-sized rifle cartridges when fired from a levergun.