I haven’t had time to try it yet. Maybe this evening. If the case holder already hits the bottom of the die, how does the lock ring on the bottom change the stroke? The case already enters the die, just doesn’t flare it. Wouldn’t I need a shorter body die, or grind the end down?
If your die is touching the shell holder, moving the ring is not going to help.
You may have to get a different set of dies.
I could see where a .45 ACO die set might not allow the stem of the expanded to screw down the extra ~.150” needed to work on the .45 GAP. Although some brands might. The sizer die would not make difference, but expanding and seating could.
Depending on the die, you might make some mods to make it work. Cutting a bit off the top side of the die, thin the underside of the expander stem, thin the jamb nut, etc. “Maybe” take a bit off the bottom. But that could cause issues going back to ACP. Also you likely have a carbide ring there which would prevent a bottom mod.