Not really crazy expansion when as you said the slug hit hard bone. What would be really nice if you could get that expansion on a chest shot on a squirrel or rabbit or other small game. As I have said in the past just any pellet and certainly any slug expansion will kill on a head shot on a squirrel of other small game. What we are looking for is expansion on soft tissue so we can take chest shots for example on grey squirrels we want to recover and not have run offs. I think the FX Hybrid slug are getting better expansion the the typical slugs. Then again the .25 caliber makes a pretty big hole which kills better in general compared to the .22 caliber. Looks like you had a good day squirrel hunting. If you get the chance try a chest shot on the next squirrel hunt and see how it puts down the squirrel. I have not gone squirrel hunting this year but I have been shooting pigeons with my .25 cal FX Crown using the NSA 26.8 grain too and they do pack a wallop. Bill