frey said - I believe the "dimple" philosophy was intended to help "pin" the case in the chamber just before ignition to reduce the possible vibration of the heavier strike.
I think what Calfee was actually trying to do with the pre-dimple was to create a shape under the pin that acted like the big dimple in Federal cases. Comparing the size of the two dimples, and considering how burning proceeds across the priming compound shape, you would have to come to the conclusion that Calfee is a little in error with this idea. That's not say his shape is wrong, he's just wrong in his analysis of what's happening.
If you compare the actual shape of the priming compound in rim fire and center fire primers, and then study how burning has to travel through these different shapes, you will see why it is more difficult to get good ignition in a rim fire as compared to a center fire. This difference in "burn time" also explains the difference in uniformity between large and small center fire primers.
We know that it is energy, rather than momentum, of the pin strike that determines how well ignition will occur. Assuming that you can't have too much energy (forgetting vibration for the moment), then it makes some sense to add weight to pins, as long as, at the same time, you also increase the spring load. Probably Calfee's approach (I guess this is his approach!) of adding weight and then testing to determine if accuracy is better, is a good approach. He is simply testing to determine what combination of energy, vibration, and lock time is best for the different shooters; position and bench rest. How he describes what he is doing is sort of odd but I guess we are all "kinda odd".
