The .45 ACP headspaces on the case mouth in an autoloader and to some extent on the extractor. Since the GAP is shorter, it would depend entirely on the extractor to headspace correctly which would be an iffy proposition if you plan on shooting it in a autoloader chambered for .45 ACP.
You could shoot them with no problem in a .45 ACP revolver as long as you used half-moon or full-moon clips.