anyone with any experience loading a 300 win mag with a starting load of powder and about a 150 gr bullet then firing it in a 458 win mag to open up the case then run the case thru a 458 sizer, I am thinking about doing this as 458 case are impossible to find. Norma, Hornaday are not making them anymore for reloading and I am going to buy factory ammo just for the cases. I did this before with the 375 HH case to make Lott cases years ago never tried 300 to 458 before. any thoughts? thanks for the help Jim

Pretty expensive

https://defendersammo.com/product/458-win-mag-brass/

they do not have any in stock and do not have a production date based on up coming demand

that is the reason I was thinking of fire-forming 300 win mag to 458

FOUND SOME
https://coastalfirearmshop.com...er-magnum-box-of-50/


can be done -- might take a could neck up steps, like 338, 358, 375, 46 expander buttons-- and ANNEAL the brass a couple times

easier to start with hh basic brass or 375
https://www.natchezss.com/nosl...-375-hh-25bx-no11930

I have made .375 H&H AI outa .300 H&H cases with one annealing and progressively larger expander buttons so I don't see why not.

I would advise every time you neck up bump the expander button into the case a couple of times instead of one quick push and of course lube the inside of the neck.

Hip

I have 50 new pieces I could part with.