I don’t think the “detonation” is because of “more oxygen”.This is fascinating, I empty 1/2 the powder out of a cartridge, result more oxygen and greater velocity.
This has been proven with slow rifle powders, you get detonation, the preassure is so great that the action fails.
Rather, there is so little powder in the case that the primer flashes the surface of the whole powder column at once, rather than progressively from the base to top. Doesn’t sound much, but it is a far bigger surface area that starts to burn, and FAST. Hence the stupid pressure that results.
