Rocky, I believe that what powder remains can't fill the void fast enough. The grains are smaller and present much less surface area, and this limits gas production, and once the pressure curve begins to fall off, the burning rate falls rapidly, compounding the situation.
What's this "tail-off," and if it is a minor and short lived event, then why does the curve remain convex for about .3 ms, which is on the order of the pressure rise time recorded?
FTR, I didn't claim the bullet stops accelerating; it most certainly keeps accelerating! The acceleration is why the pressure-time trace is flatter than the pressure-volume trace. It's because the acceleration is due to the pressure that I'm confident switching from a p-v curve (which I'm certain must be concave upwards) to a p-t curve will still leave you with a curve that must be concave upward (after the burn is done). Real curves are convex, so I believe burning continues--as QL predicts.
