Iagree that it would be a HIGH pressure spike. IMO, This looks like smokeless powder, cracked just enough to smoke a little. But when it comes to heavier bullets without sabots to ease the initial launch, that's when the High pressure spike will show itself[&:]

Think about it.....It says TIGHT fitting sabots, FIRMLY packed powder charge, SEALED breech plug---for best results. This is to harness that progressive burn pressure