I don't know what distances you are hunting at, but for close work maybe a 17 with trail boss would work good. I haven't tried it in a 17 but loaded at that slow speed it might sound like a 22. With a heavier bullet you should retain enough energy for squirrels.

edit: I saw you said 150 yards, a couple posts back now. That would be a little out of range. I posted on your other thread too about the 17 ccm, you would need a custom bolt face. Maybe look into the 17 bumblebee, it is a cut down bee case so the capacity is right in line with what you are looking for.