RE: Killing a Squirrel : BB or Pellet Gun?
I've had some heroic squirrelsgo pretty farafter being shot point blank in the chest with a BB gun. Nothing like having your neighbors watch as a mortally wounded squirrel half runs half crawls across the street bleeding everywhere.
I never thought I'd have to consider something "not enough gun" for a squirrel but I'd go with pellets.
.22 short is what I use now.