I would find it hard to believe that 5 good hits with stingers didn't yield a quickly dead skunk. If this is the kind of thing you normally shoot with your 22's, I would suggest trying CCI Velocitors if you want to change from Stingers. I would prefer to use high speed rounds versus the SV loads (target) if the rifle is sighted in with them. The CCI SV rounds should be more accurate.
I have not had any problems with Stingers, but I don't shoot them often either anymore. That is a fairly long shot in my opinion. Most shunks are dispatched at pretty close range. But in my opinion, under 100 yds and you should be fine with Stingers.