system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the military want a multi-caliber rifle for snipers

I don't see why anyone would want to change the caliber in the military.  Don't you always want to train with your 'real' equipment?
I can't see why you would not always go with your biggest caliber.

*Edit* I am talking about the new US army PSR that shoots 308 300win 338.
gpt
The largest weapon is not always the best, like the largest hammer or the largest shovel isn't always the one to use. A smaller round might yield a lighter load on the soldier, more ammo capacity, an easier rifle to fire without beating up your shoulder... Any of a variety of reasons would compel someone to use a different caliber.