There are plenty of places here in Colorado that stock 300 WSM. Sportsman's Warehouse has several brands and bullets weights on the shelf as well as Wal Mart.
I am just back from Craig Colorado scouting my elk tag area and all the stores I visited there have tons of 300 WSM on the shelf.
I purchased an FN PBR back in 05 from CDNN as a barreled action in 300 WSM and stocked it with a McMillan Model 70 Super Grade style. Rifle shoots like a dream and I have fired many rounds through it. I see not problems with the cartridge.
I don't see any problems finding the ammo anywhere you choose to hunt.
