I've used them for YEARS. The CCI .22 rimfire shells have a protective "capsule" that keeps most of the shot from contacting the barrel.
Never the less, they are dirty, but a decent cleaning will take care of any bore leading.
I carry a S & W Airlite eight shot .22 on my farm. The first three chambers are loaded with the Speer shot loads, the rest Quick-Shok HP loads. Very useful. The loads contain appx. 1/12th OZ. of # 12 shot, commonly called "dust" shot.
The .22 loads are only effective to five or six feet (not yards), but will put the hurt on a poisonous snake.
Much better are the .38/.357 loads, They contain about 1/4 ox, of #9 shot.
I feel the shot size is a bit large for the shot count, so I handload # 11, or # 10 in the .38 cases.
Copperheads/water moccasins are DRT (dead right there). I mean they are stone cold DEAD.
I had an experience a few years ago, in which I shot a large water moccasin with a .22 HP. The low shot propelled the snake upwards, and towards me, with the after effect that I nearly was wearing a snake "necklace".
The shot won't do that.