Now looking at these side by side pictures, the question of using the 7 Rem as backup ammo if all is lost in transit is answered. It can be done but is a not good idea except in case of emergency.
At the range one day a fellow had a mid-50's rifle that he had inherited from his Gfather. I asked what it was and he said 7 Magnum. I looked at the brass, he was shooting 7 Rem in a Mashburn chamber. I asked why and he said he could buy the shells locally and they worked. Accuracy wasn't stellar but in a pinch in the way backs with lost ammo/luggage.
