by your definition of european caliber being obscure most of my rifle cartridges are exactly this

6,5x53R
6,5x57
7x57R
8x50R Lebel
8x57IS
8x58RD
9x57
9,3x53R
9,3x57
9,3x64
375NE 2,25"
401 WSL
10,75x57
10,75x68
11,2x60 Schüler

BP needle fire cartridges

9,5 mm Dreyse
11mm Chassepot
11mm Dreyse
12,3 mm Dreyse
16,5 mm Dreyse

center fire
28/46 rifle cartridge

and not forget 9 mm Flobert rimfire and 4 ga pinfire and beside of the common shotgun caliber a 24 ga

I think only the 7,62x39 and the 22 lr are not obscure