I have yet to see anything reasonable that my .17 will not destroy. It is accurate to ridiculous rimfire ranges, i'm planning on taking some steel/alum. plates to shoot at for some serious penetration testing when i have the time in a week or two. When I get around to it I'll post results. I only shoot the ballistic tipped Federal/Hornady in mine. I lose about a 1/4" off my groups with the hollow points. I think its overkill for squirrels honestly though. I nailed an average sized gray squirrel at about 65-70 yards and the entry was about quarter sized, exit was from its armpit to its hind legs with all the entrails hanging out. Luckily it didnt hurt much meat though.