The 338-06 brass is available headstamped. It is made by Norma for Weatherby. Midway carries it as I'm sure others do.
I have the 338Win Mag in a 15" barrel including brake that is a pussycat to shoot. Im shooting 180g Nosler Ballistic Tips at 2840fps.
The brake on my barrel is removable so I have shot it without the brake for comparison. It is a definite handfull but very shootable.
As a matter of fact I'm just starting to do some serious reloading for my 338 and 300's. They are both 15" with brakes. My shooting and reloading has been neglected far too long. It's time to remedy that.

Ronnie