It's likely Ackley Improved but just doesn't state it. But it really doesn't matter, since you have to fire form the cases anyway. Just don't fire regular factory Roberts ammo through it if you are worried about case head separations. If you are REALLY curious, you could do a chamber cast, but I think its simpler just to do one round up using standard case forming procedures and measure it after you fire. Then you can send the fired case off to have custom dies made if it's not one of the "regular" wildcats.

Just don't lower the fireform charge too much, or the primer setback (actually it is case "blowforward" by the primer ignition pressure) won't be overcome and you WILL think you have excessive headspace when it's really not there.