Piezo Electric pressure measurments.........
In the May 2009 issue of Shooting Times magazine, there is an article explaining the new piezo electric method of measuring cartridge pressures. Of interest is the fact that the old CUP (Copper Units of Pressure) measures peak pressure only, while the piezo electric measures the pressure curve from popping of the primer to projecting from the muzzle.
Using this data, powder manufacturers are developing powders that eject a greater mass of gas while staying within the acceptable pressure/burn rate for certain pistol cartridges. This increased ejecta gives extra downward thrust through muzzle compensators, helping keep the muzzle down upon firing.