you can't get too light or the action won't cycle right and you'll need to taper crimp instead of roll crimp. I have a seperate taper crimp die so it adds a step but it doesn't take that much longer. I think I read somewhere that if you buy the Lee factory crimp die it's a roll crimp for revolver and taper for the autos. .45 ACP headspaces on the case mouth that's why the different crimp.