I have use the contender .410 since 1969 for squirrles and rabbits. You are wasting your time using it for squirrles unless you are within 10yds. If the critter is 50ft up a tree he will just laugh at you. If you catch one on the ground, at the right distance, it will do the job. For rabbits, yes, they are easier to kill. Also, you usually can get much closer to the little thing. The .410 is marginal, at best. But, if you get close enough, it will do the job.
If you really want some fun, try it with clays. Be careful!! It is very easy to point in the wrong direction.