A book I had told of the murder of a government official by a hiway man with a blunderbus. An autopsy was done on the guy and was found with five ‘pistol balls’, through him. Liver and lungs were hit and mortal. One fat ball through lungs or liver would likely have been mortal too. I doubt even today any .45 and up ball delivered from a blunderbuss size shoulder gun would cause death before help could be gotten to him.I never really see the need for buck shot...at the distance it is reliable it would be easier to just use a ball!
So dead is dead.
However I wonder if it’s more incapacitating. Shot guns were used in the trenches of WW1. Would a man hit with a load of buck shot be less able to return fire or bayonet thrust in that time between hit and unconsciousness?