As for N, the way I see it, you have to assume a lot more in order to say that N is likely to be an unpleasant experience. For instance, if this is true, all countries that offer euthanasia to their citizens and all organizations advocating for it are lying about their observations and leading people to a painful death. What would they gain from doing that? Why not use nitrogen or helium?
No not at all. Nobody's lying here. All good sincere intentions.
What I'm saying is consider the possibility that even if the subject is unconscious, it may not be painless at all. This is the outright destruction/end of the body and all biological processes.
The body even if we are not conscious will fight to the end. This is demonstrated on many of the end moment videos out there if anyone cares to look.
If we are talking about the same N, those 10 minutes, and 30 mins of dying (up to 8 hours pending on the subject) may not look like much to the outside observer.
Maybe some death rattle, body goes waxy discolored, and stiffening. However, to the subject it can be a world of suffering that cannot be articulated.
For example, As we saw with Smedley, he was suffering until he fell unconscious. Then it seems that the video was cut off prior to getting into the death rattle out of respect.
Just because the body is unconscious doesn't mean we don't go through the same biological process of dying. Nobody will know the feeling except the subject themselves.
Chemically speaking, if we subcribe to Sean Caroll's theory, the meaning of life is to hydrogenate carbon dioxide. Entropy driving this. It's not unreasonable to think our body evolved with the function in mind and will fight like hell to hold on...which can mean a lot of pain.
That said, shotgun aimed right is close to the fastest and arguably more convenient method. I'm saying we should do better and reduce the "what if" timeframe to near zero. Not the avg. 10-30 mins of "unknown level" pain with N.