“After much study I’m convinced the role survival rifle is best filled by modern medium to large bore air rifles.”
What would you recommend?
The two most appropriate types for taking small game silently would be the pre-charged pneumatic (pcp), or a single stroke “springer” (the most popular of which are actually powered by a “gas piston”).
Each type has advantages that must be weighed by the end user. Lots of helpful info on YouTube, and at airgundepot.com, or pyramidair.com.
I’d ignore the .177 caliber and start with .22 up to .50 caliber. Most pcp guns .357 caliber and above can also shoot “air bolts” at velocities higher than any crossbow on the planet.