The other point Dave is that while you may find some 300WSM stuff, there might be little if any variety. At the same time it is quite likely there'll be several different varieties of 308, 270 or 243 on the shelves at even the most modest gun shop.
Jeez down here you could go hat in hand to nearly any farm house and ask, and they'll likely be able to produce some 243 ammo you could use in a pinch! I doubt you'd be able to say the same re WSM; you'd likely get nothing but a confused look.
