[SvilleKid]

I've never made a punch from a .45, but have half a dozen from .270 and .30-06 rifle rounds. I found that these work best when the edge is well sharpened, but which still leaves a slightly saw-toothed edge. The secret to using them in this state is to gently rotate the punch back and forth, verses using as a pure punch. This consistently produces a clean cut for me, never had one tear the wrapper. I have a set of cheap jeweler files that allow me to sharpen the inside edge once I get the outside edge to the shape/sharpness I want. You are right that you will never get the soft brass sharp enough to use as a punch. But modifying your punch technique to what basically amounts to a hole saw style should give you desirable results. The longer rifle casings do make it easier to twirl the casing back and forth than with shorter pistol rounds. I also find that punching the primer out can give you a good route to push the plugs back out. Then, buff the casing to a luster, and clear-coat with clear Krylon. Keeps the casing from tarnishing.

If you want, PM me for my addy, send me a few spent casings, and I'll try my hand at making some up for you.