i have a wby 30-378 mk 5. i am considering re barreling and going to 338-378. is there a way to resize all my brass to tie new caliber. i know it is only the neck that is different. wby brass is too expensive to not try something

Might discuss this with RCBS to see what case forming dies would cost. Unless you know of someone else who specializes in case forming, RCBS is the only one I know of who provide this kind of service. Best wishes.

I'd think that with a good resize lube such as Imperial sizing wax just carefully running them thru the 338-378 sizing die might work.

Probably is a good idea to check with RCBS though.

That is a great elk cartridge.