An easy way I have found to make custom sizer dies is as follows: start with a piece of flat steel plate and a short length (about as long as the case you want to size) section of steel tubing, an inch or larger ID. Turn an exact replica of your proposed case out of some sort of free machining steel. Either turn and thread or drill and tap the back end for a small threaded stud, and drill and tap the plate for this so you can firmly attach the case to the plate. Now locate and clamp the tube over your case, easier if you machined a groove in the plate beforehand but not absolutely critical. Now use some zinc casting alloy, or babbit metal or some sort of hard castable alloy and fill the tube to just below the mouth of the case. When it's hard, remove and face off in the lathe. You now have a sizing die you can use in a vise, knocking the cases out with a rod. Beyond this, you could get somebody with a small boring bar set to chamber a sizer for you that you could use the same way. BTW, I have seen a 22-25ACP setup before, in a Romanian '69 bolt action I believe. Cute little squirrel rifle! A .17 would be cool, but a .14 would get spendy for the barrel and bullets I'd imagine.
