Most of our F class guys use Winchester brass for 300WM's. A friend of mine took his new GA Precision to the 1K line last month. After his first match he decided to shoot 10 blind, with no spotters. Of the 10, I could cover 7 with my hand (fingers closed) and the three outside were still under MOA, verticle spread of less than 4". It was really a very nice group, shot from a 24" barrel, off bipods, with virgin brass and a 10X Leupold. I'm convinced Winchester makes the best US made brass.
Lapua is hands down better when it comes to out of box consistency and appearance, but I haven't found it to be any more accuarte so far.
FatBoy...