That's what I did this past December.  I found a place in Gettysburg that had a stack of Remington so I bought a few boxes.  Then as I was making a second pass through the store I saw they had a few boxes of Winchester 30-40 so I bought two boxes.  I don't have any Winchester and wanted to see how it shot compared to Remington.

I figured out that loaded ammo is my best shot at finding brass as expensive as that is.