These guns use an adapter/chamber sleeve to be able to fire multiple calibers. There are break open single shot shotgun out there that does this. Check out X-Caliber X-treme and Chiappa X-Caliber

Great article on modern survival website here
https://modernsurvivalonline.com/top-multi-caliber-guns/

Tyler, I would look at TNW : tnwfirearms.com/product-p/asrx-cplt-9445-xxxx-xxxx.htm

They only way to shoot multiple caliber with a bolt action rifle is by using a chamber adapter/chamber sleeve. The bullet diameter has to be the same.. .22LR, .223, and 22-250 are all 22 cals so that's why they work. Theoretically, with a chamber sleeve you could shoot a 30 cal bullet out of a .308 with the adapter.