RE: Variflame adapters and 25acp?
I don't have one like that, but all you would see is a hole the same diameter as the 25 ACP case and deep enough to seat the case as far in as you want it to go.
The bottom of the hole has a slight taper that matches the taper on the point of the drill bit used to drill the hole - or you can make the bottom flat by finishing it with a bottoming bit.