I'm wondering the same thing, Paul. The .17HMR is a great squirrel gun as long as you head shoot them. Anywhere else and you're going to be destroying lots of good meat. The 20 grain game points aren't quite as bad but still do considerable damage. The mach2 also does it's fair share of damage but not to the same extent as the HMR. Still, they both blow squirrels apart much better than any .22 ammo I've ever shot. That includes CCI Stingers and my personal favorite, CCI Velocitors.
Maybe I'll have to take my Thompson .22 and my Mach2 out for a hunt this weekend and get some comparison photos.