New invention, sunray, called a "lathe". Works great.
Another new invention is a thing called a .300 H&H casing.
Put the two together.
RCBS makes dies, too.
MOST .280 Ross original factory ammo was loaded with .284 slugs, too.
ONLY round I have found actually USING the legendary .287 is a single round of .28 Ross-Eley experimental.