As mentioned, a given amount of a powder will produce only so much energy regardless of how it is ignited. In a pistol or rifle barrel the difference is in the "quickness" of the ignition. It is also greatly influenced by the expansion ration. In pistol cases with the faster burning powders they are ignited and burn very quickly so there is not much difference regardless of the ignition. However, with slower burning powders such as with HS6 and the VV powders we begin to see the difference in ignition between the primers. The milder the primer the slower the ignition and burn is so the bullet moves further into the bore which increases the volume for the expanding gas to fill, thus the time pressure curve is slower with a slightly less max psi. With the "hotter" primers the ingnition is more intense resulting in the fast time/pressure curve and a slightly higher max psi.