I shoot both Colibri 20gr 420fps and 520fps through a suppressed bolt action 77/22. The only sound you hear is a hammer click, and the hollow thump of it hitting the body. They feed fine off of the rotary mag, but I don't think you will be taking a cat out with a single shot unless it is extremely well aimed. I've witnessed a squirrel take 3 rounds to the body and still moving very well. To the head or chest it is pretty effective.
If you want DRT, head shots recommended.
If you want them to run off and expire, body shots.