I have seen that business about starting a fire by pulling the bullet, dumping the powder, then igniting it by firing the primer. Or not. When I tried it with a revolver, the blast either blew the powder away instead of igniting it or the powder flared up and went out without igniting the kindling. Plus it is not that easy to pull handgun bullets.
With a rifle there was not enough primer flash at the muzzle to ignite anything. Maybe it could be done with black powder or some gun I didn't try, but it does not seem a really reliable way to start a fire.
FWIW, I suggest a camper/hiker/hunter who might have to start a fire carry a couple of BIC lighters. Much better than the old match case and beats trying to ignite powder with a primer.
The "spark" from dry firing as described in this thread is not hot or long-lasting enough to ignite any kindling, and I doubt it would even ignite a flammable substance like methane or propane.
Jim