LOL! Wow, a lot of fuss over a .22LR!
I've used everything from Remington green box regular old lead rounds to CCI HP and Remington Yellow Jackets HP, and they all have one thing in common - they kill squirrel and rabbit.
Yesterday, I picked up a brick of Fiocchi .22LR because I know that company kicks out accurate and reliable ammunition in .45 and .308, so it only made sense that I would buy their .22LR lead round nose. Nothing special, just accurate. Compare the lead from a .22 to the squirrel's little body and you'll not be so worried about HP or LRN. I've dropped a lot of squirrel and rabbit, and never lost a single one because of type of bullet.
Get a rifle, get ammo that is consistent and just get good. Ammo type is for human preference and argument, the little critters hate them all!