Imagine the body is sitting in a chair, like an electric chair.
But the head has put in a mask to limit movement.
That is inside a box.
At the other end of the box are two tubes for a 50 cal round, rapidly expanding to hit the cranium.
Guaranteed not much is felt nor for long. It exceeds the speed by which the body can sense things or communicate a signal.
All left over debris is contained by the box which can either be incinerated, buried with the corpse, or cleaned and reused.
I have the opposite view. A very slow and agonizing death. Televised as a warning to wannabe murderers.