Killed a lot of squirrels with .22 mag, if your going to stick to head shots which is what I always did it doesn't matter.. but if you take any type of body shot a solid/fmj bullet is best as the .22 mag will blow the whole front end off a squirrel if any bone is hit.
CZ`s are awesome little guns owned 2-3 of them, one was a .22 mag.
I would just stick with what your using as they are plenty accurate, might try some longer shots just in case also.