CCI has made something called a CB Long since the late 1970’s. They use a 29 grain .22 Short bullet in a .22 Long Case. Only has a few granules of powder. Rifle velocity is a little over 700 fps. They are harder to find in stores than the CCI CB Short version. You may have to mail order them.
Advantages over the shorter case version are that they feed perfectly thru box magazines, and will not leave a residue ring 2/3 of the way inside the chamber like short-cased ones will after extensive shooting.
They will kill squirrels and rabbits with perfect head shots, or forward rib cage shots. Be considerate of the animal. Chose your shots carefully; keep them under 20 yards. Not as much margin for error as regular .22 LR ammo.
I have fired approximately 20,000+ of them in my lifetime; sometimes hunting squirrels, rabbits, and snakes. Killed thousands of pest birds ( starlings, sparrows, crows, etc. ) with both the short and long versions. Much prefer the Long. Probably another 8 to 10 thousand ( mostly birds ) with various full-powered Long Rifle ammo.
Needless to say the CCI .22 CB Long is one of my favorite and most useful rimfire cartridges.
I like the .22 Magnum a whole lot too, in a rifle.