Re: Which brass works for you?
Lapua stopped making 300 WM brass about 12 months ago, to the best of my knowledge and belief. There still may be some on the shelves somewhere though. I believe RWS still makes 300 Win Mag brass, and that's as good as Lapua, but you probably won't find it locally. You'll probably have to search the web and order some that way. Lapua or RWS brass will cost ~ twice as much Winchester or Remington.
If you're looking for the lowest cost brass, just go ahead and buy some Winchester brass. Not as tough, or dimensionally consistent, as Lapua/RWS, but it'll get the job done.