BM1455, my apologies for not paying closer attention to the forum.  Thanks very much for your comments.

The powders and loads I have chosen are because there is information on the Hodgdon web site about safe reduced loads with these two powders.

Wolfe Publishing has an excellent CD with ballistics information taken from a study at the University of Minnesota around 1950 by a guy named Brownell. I don't know if there is a connection to the Brownells vendor or not,but, in any case, he demonstrated that Secondary Explosive Effect is a harmonic reinforcing pressure wave inside the case which occurs when the powder volume is low and the burning characteristics of the powder are slow. If the case is full of powder, the harmonic is attenuated ( even though there are tiny spikes in the pressure inside the case on every shot ). When the powder is slow and the powder volume is low, the pressure can more than double. The effect is difficult to reproduce because is does not automatically occur with some given powder at some given load.

I definitely support safe loading by only using recommended loads with dependable data. In this case, the loads I am using are specifically documented as safe for reduced loads by Hodgdon for these two specific powders.