I currently have a FX Impact .25..I originally sighted it in at 50 yard, but have been taking many shots at the 25-30 yard make..I seem to have one problem, and I am not sure what is taking place.. I have shot three squirrels square in the chest only to have them run off before they expire.. I would have thought that the impact from a JSB MKII @ 886FPS would deliver the crushing blow that should stop them dead in their tracks..I can only think that the pellet is passing through without mushrooming ??? Any one care to weigh in on their thoughts here....