Sorry, I should have been clearer.
My point is more about market penetration and wide usage than what came first as a strict technical development.
So, what I'm saying is that there are various rounds that have similar performance, often achieved in different ways and coming from slightly different stand points.
7mm seems to be a popular calibre to develop as for many shooters it seems to be about the "sweet-spot", for deer sized game at least. (And before the pedants jump on me, yes, I am making a broad generalisation).
So 7mm be in energy terms:
Fairly mild eg:
.270 Win (I know more like 6.8x64 in terms of the metric system but I think ballistically so close out on an off the shelf sporter with factory ammo we're splitting hairs)
7mm Magnums - Various.
My apologies again for the generalities to the cartridge pedants but that is what the OP started the thread with so that is how I answered.
Enjoy your shooting (that means leaving the books and reloading room!)