Sorry Drew but your above text does not substantiate why finely ground smokeless powder will detonate rather then burn. From my research I have not found any source to say finely ground smokeless powder will detonate. Actually it is just the opposite the sources say finely ground smokeless powder does not change the burn/explosive properties of the powder. What can happen if the vibration of the shell is enough to cause the powder the grind smaller is what you (Drew) have explained. Now there are void spots in the shell which may cause pressure variations BUT it does not change the chemical or physical properties of the powder causing it to detonate rather than burn.
Drew I have gone back to what you wrote and I am uncertain what "secondary Explosive Effect" actually means. As I understand 'Effect" it may be similar to an explosion and cause the same result but it is still not an explosion.
