A very nice gentleman from Washington state is selling lots of 50 unfired but carefully prepped 300 win mag brass over on ebay. I can't vouch for the work he's put into them because I haven't seen it yet (I bought one lot last week).
If you do a search for "300 win mag" you'll see them/it.
Roger
If you do a search for "300 win mag" you'll see them/it.
Roger