Just for conversation,
What is the definition of a large caliber rifle?
Caliber is a decimal equivalent of the bore diameter, I.E. a 30 caliber rifle has a .300 diameter barrel, so in order to be large caliber the rifle would need to have a barrel diameter greater than .500 so a BMG 50 by definition would not be a large caliber would it?
In order to be large caliber you would need a .600 nitro magnum.
Further a .308 has less down range energy than either a 1906 30 caliber spring field or a .270 which is a necked down 1906 30 caliber spring field.
The .270 caliber although it has substantially more down range energy than a .308, and under certain conditions, loads and at certain distance more down range energy than the 30-06 would certainly not be a "Large Caliber" rifle as the cross sectional bore diameter is only. .270 of an inch.