Say a rifle manufacturer has a new rifle model out.
they come with a choice of wood or vinyl stocks
stainless or blued barrel
varmint or sporter profile
that is two stocks each in two profiles and two barrels also each with two profiles that need to be manufactured
a variety of twists to suit but a lot are 1:10"
then they offer chambering from .243, .260, 6.5x55, .270, .308, .30-06, 300WM etc etc
so you have two action lengths and a variety of bolt face sizes to match cartridge.
I am making the assumption that the only difference between the barrels is once they have been chambered.
They take a .30 calibre sporter barrel and and chamber it in .308 or .30-06 or 300WM
Now my question (after a long ramble!) is:
What makes a barrel with a fixed external profile a 62,000 psi, a 60,200 psi or a 64,000psi rated barrel just because the chamber is different?