Was he talking about the .30-338 Lapua, or the .30-338 WinMag?
If he was talking about the .30-338 WinMag, then it IS based off the .300 H&H, just like almost all of the belted magnum are (other than the .378 Weatherby cases, which are larger in diamter).
I will assume you are referring to the .30-338 WinMag. If that's the case, all you have to do to make brass is run either 7mm RemMag brass or .338 WinMag brass through a full-length .30-338 WM sizing die. And you're done.
Here's dies for the .30-338 WinMag...
Redding Deluxe 3-Die Set 30-338 Winchester Mag
The .30-338 Lapua is derrived from the .338 Lapua case, which is NOT based on the .300 H&H. And to form brass for a .30-338 Lapua, you just simply run a .338 Lapua brass through your full-length .30-338 Lapua die.
Redding 3-Die Set 30-338 Lapua Mag
"I'm just a peckerwood who lives in the hills with too many guns..." - Bob Lee Swagger
"Give me a minute...I'm good. Give me an hour...I'm great. Give me 6 months...And I'm unbeatable." - Col. Hannibal Smith
Originally Posted by WildRose
The 284 is to the STW what a tricycle is to a Ninja.