Man, you are consistent!
A few years ago I decided to try some factory 7x57's out, to see how they compared to 7mm-08 factories, since people keep saying how 7x57's are loaded down so much. I tried one local store here in Montana and found three brands of 7x57, equally the variety of 7mm-08 ammo on hand. (Turned out the 7x57 stuff was a whole 100 fps behind the 7mm-08, on average.)
I would bet serious money that you'd find more 7x57 ammo on gun store shelves in most parts of American than ammo for the .358 Winchester, the cartridge you keep holding up as ideal.
