I can't comment on Norma brass for 300 WM. I use Norma 308 brass for my competition loads. I personnally like Norma brass and will continue to use it. I had 8 loads on the Brass before I annealed the necks.
I only use Weatherby brass (made by Norma as we all know) in my 300 WBY and I couldn't be happier.I monkeyed with some other brands a bit but the Norma made brass was by far the most consistent and long lasting. On the low extreme I had some Hornady that the primer pockets gave out after 2 reloads and at the other extreme I have some Weatherby that just had its' twentieth firing!