I have not experienced any failures to fire in the last several decades. I limit myself to CCI standard velocity, and fire out of quality clean firearms, most often Ruger MK II, S&W K-22, Colt 1911 .22 Conversion on a Series 70, and Winchester 62A. My worst problems are keeping the K-22 cylinder clean enough to not bind, and keeping the Colt 'floating chamber' floating, but the remedy there is to clean them well after several boxes of ammo.
So, my variables are very few, but my success rate approaches 100%.