You are aware there are already reamers and dies made for other wildcats based on 357 Max cases right?
http://www.mygunroom.com/dvgunshop/calibers.htm
quick google here
http://castboolits.gunloads.com/showthread.php?p=290416
Trim a new 357 maximum case to 1.36" and then size it with 300 Whisper die. This would give you a rimmed version of the 300 Whisper. Just use a standard 300 Whisper Reamer to chamber your 30 cal fast twist barrel - the Aussie's did a lot of this kind of stuff and Bertram even made 222 rimmed cases.
http://www.midwayusa.com/viewproduct...m_campaign=652