Miller,
I have killed perhaps two or three 3/4 ton pickup trucks full of squirrels, 99% of them with .22 shorts. I used a Remington 552, a gun that will fire all the different lengths of .22 ammunition and interchangeably. Id be willing to bet that at the bench, the standard velocity long rifle stuff would be more accurate, but, shorts are accurate enough. Put a short through a bushy tail on a high branch, and 99 times out of 100, it knocks his little ass out of the tree. They are quieter, also.
My Remington 581 also handles .22 shorts just fine.
I retired from squirrel hunting when Dad started goose hunting, and he began leaving my Moms Irish Setter, a show dog that would hunt, at home.
We had a lot of fun.

Best,
Ted