This article indicates there’s no difference, in fact, and is lower than the conservative percentage I was getting earlier.
Maybe I’m reading the abstract wrong, but it appears that the article specifically compares single headshots with multiple GSW including a single head GSW. In which case there’s no significant difference.
But maybe I’m reading it wrong. I may be biased, because I really want to believe that JimBob shooting himself in the foot cleaning his gun, occurs with a higher frequency and with less mortality, than people shooting to kill.
I admit I didn’t look deep into that particular article. There are a lot of sources easy to find that show that multiple GSWs are surprisingly not that much more lethal, but they’re harder to repair. This one for example which lists 13% for single, and 18% for multiple.