My experiences with chest shooting fox squirrels with a .177 air rifle lead me to believe that you really need an EXPANDING hollowpoint pellet (read that Crow Magnum and Predator) from a high velocity gun from a high velocity gun (over 900fps preferable) to get CONSISTENT quick and clean kills. Mind you, fox squirrels get up to 3 pounds and are unbelievably tenacious. Also, I fully realize that sometimes domes and lower powered air rifles can get the job done quickly but from what I've seen, there are almost always mitigating circumstances that allow this to happen. For example, a grey squirrel or a red squirrel are substantially smaller than the larger fox squirrel. Another consideration is that NOT all chest shots are equal. A .177 dome that hits a squirrel in both lungs will take some time (sometimes alot of time) to kill. If it hits one lung or nicks a lung, it can and will take even longer. However, if that same pellet instead hits an artery high in heart or through the top of the heart AND lungs, the effects on the squirrel will be immediate. Same thing with a shot directly through the heart. Small game don't make a "run" when hit through the heart like a deer. The problem is that the heart is a very small target on a squirrel whereas the lungs is a very generously large one. There ARE airguns and pellets that will take even fox squirrels with lung shots. Some can even do so quickly with a one lung shot. A gun/pellet combination that can take squirrels with lung shots (and I mean expiring under 10 seconds and under 10 feet bare minimum) will take ANY heart/heart artery squirrel to be sure but the opposite is not always true. Fox example, I wouldn't want to use a Beeman R-7 with an pellet to chest shoot a grey squirrel, let alone a fox squirrel EVEN THOUGH a heart shot would turn them off immediately. Too much chance of missing the heart---and even if the pellet did get the lungs, I would want more, much more tissue damage to those lungs than what the little rifle could provide. With such a little rifle, brain (not head--brain) shots would be necessary.