There certainly have been moose killed with a 22, usually long rifle, but it is obviously, in no way, a suitable moose cartridge.
And here is some fact, not something I read, or something someone told me. A broadside shot at a moose at forty yards, with a 22 long rifle, will not penetrate to the lung area. The heavy hide and meat under the hide, will stop the bullets before they even get to the rib cage. Five shots, and everyone the same, some higher and some lower, in the side. No chance, whatsoever, of killing a moose with a 22 lr to the "boiler room."
Someone rhimed off all the top quality bullets for a 6.5 Mauser. We all know the super hyped, expensive bullets work well in suitable calibres and we all know the expense of the bullets compared to the expenses of a hunting trip are a nothing. However, that type of bullet is not needed in the 6.5 Mauser, to kill moose. The 6.5 was loaded in Canada with the 160 grain, round nose soft point bullet, and this was the missle that made the great reputation for the 6.5 Mauser, as a moose killer. As a young boy, I used to look at that long bullet, and think it was pretty neat looking, as compared to the usual 30-30 types. I also knew that the men who used the 6.5 didn't have to follow a wounded moose through the bush.