Gary hooked me up for expanding case mouths.

He must have figured it out long ago. Rather than use multiple die sets you only need a handful of the elliptical "football" type Hornady expanders for one of your die sets you already have laying around. In my .476 GNR die set I use a .373", .414", .456", and .473" expanders. They step up the .348 Winchester brass expanding it to where I can get a .476" bullet in there to shoot and fire form the .476 GNR cases. Typically you use an expander ball (for the sizing die) that is about 0.002" under the bullet you are using. This gives the "bullet pull" for the brass to firmly grip the projectile.

I wanted to try to make .401 WSL (actually 0.406") from expanded 7.62x39mm cases without firing .311 bullets from them to form. I was able to go in one careful, well lubricated, step from .311 to .375 cal. Usually a .338/.358 step at least would be better, but I cheated this time, no splits.

I didn't have another good intermediate step so I over-expanded with the .414" then used .41 Remington dies to size down.

I'm using alloy .410" bullets which are forgiving of the slight oversize. The bore squishes them down just fine. I focus on only enough power to cycle the "blow-back" counter weighted action. I've worked up to 12.0 gr. Herco and a 210 gr. cast bullet for around 1700 fps. This should be mild but easily cycle the action. I also have some 270 gr. and 300 gr moulds that work at a slightly slower speed in formed cases. The old gun works and is accurate, a total hoot to shoot, so why push it in that type of action.

The blunt SWC may not feed from the mag., I hope it does. Some rounds seem to need some bullet nose to guide them in. This firing should blow the old remaining taper out to the web.