I've been working on a 30 caliber wild cat for my 336 for several months now. The gun smith informed me that he is almost complete with the work and I should receive it in a week or so. The new cartridge is based on a 308 shell casing with the shoulder set back .1" with an AI body and shoulder profile. I've never sized a new cartridge case from an existing commercial case. Should I be able to run an unmodified 308 case into the wild cat sizing die or do I need to size the new casing incrementally?