10mm automatic 
No smaller than that.
It was designed in 1905 if that helps.
Designed by John Moses Browning ? Or is it 9mm mauser?
Designed by Mr Browning.
Goto be 25 auto then right?
That’s the one.
6.8 Remington SPC
6.5 Grendel?
Nope neither and its bigger than both of them
325 Winchester short magnum then?
7mm Rem SAUM
I’m wrong just silly guesses now! It looks like a 30 cal I was reading about last week but I’m still not 100%
I cheated I went back through what I read the other day it’s the .30 AR
That’s a 303 British on the left of your wondering
Sorry had to delete first post as there was 3 variants in the photo didn’t realise until it was posted
Goto be 280 ross right? A mate named Ross told me bout this cartridge years ago