See title. Specifically for the "high power, bolt-action rifle with a variable-power, magnified optic" mentioned in the 5 guns post , complimenting the other guns mentioned there. If you could only have one, which would it be? I know the answer is always "it depends", but what is your thought process in deciding and what works best for your needs?
.308, because it's everywhere and you likely won't ever have a use-case for the less frequently found sizes. If you find yourself pushing the limits of purchased .308, you can look into handloading for performance as well.
But the reality is .308 will work well enough for 98% of what you want to do, and the money you save by buying the most common caliber can immediately be put into the optic.
Yep, the availability argument is hugely appealing to me, this makes a lot of sense