The .22 LR in my opinion is the best gun to use on squirrels. With your choice scope's, or iron sights if you like. The .22cal is the cheapest, probably the most fun gun to shoot. A lot of people like the Ruger 10/22 which is all around a great rifle. And I own one and really enjoy plincking with it. But for the best accuracy from a .22 cal. or for that matter any rifle, a bolt action rifle is the most accurate rifle you can own. It's already a proven fact that a semi-auto use's the gas from a fired shell or cartridge to extract the spent case. Where a bolt action will lock in the shell, or cartridge, allowing all the gas to be spent on the bullet. But this is just my .02cents worth, and I know you'll get more information about what people like. Good luck on your choice of rifles.