Al Miller answered the question as a 358 caliber with at least 250 grains.
He mentioned that almost none of our cartridges today would have been considered a “big bore” in the 1800’s. (Or he said something similar.)
To me my 416 Rigby is a “big bore”. (Though it’s probably a medium in Africa) My 375’s seem big too. Bigger than 308 and up to 358 “Medium Bores???” Maybe 338 to 416 medium bores???
I guess that a caliber that is 100% reliable without expanding bullets perhaps???
There’s no definition that anyone can take to the bank. As Jorgel said, it’s a geographically challenged question”.
When we were in lower grades of grade school and dad let us shoot his 1903 Springfield and with cast bullets, we definitely had just shot a “Big Bore!”
It sure was big compared to our single shot 22’s.
I have a couple of 45’s - a 45-70 and a 45-90. I’m don’t think they are in the same class as even a 375 H&H - so to me it isn’t just about diameter. (Maybe I’m hedging here a little).
Last edited by Bugger; 02/03/18.
