OP,
That's a whale of an idea ...... thanks for sharing!
You've made me get my thinking cap on!
Not to steal your thunder, but to add to it .......... I am wondering about a different fixture and bottom anvil to cause brass to be upset a little deeper into the pocket?
Right now, I assume you are moving the brass at the pocket opening for the most part but I am wondering if a receiver base and an adjustable hardened screw from up through the center of this base with a tip shaped not convex like a steel ball but concave like a rivet set punch to deepen the brass displacement.
Also there are punch sets for center finding ...... they have a "raised tip" that would "find" the inside flash hole with an otherwise flat face .......... I just happen to have a set of them, I'll have to see if they are too much of a good thing however.
..... I'll be visiting your system ........ you can bet on it!
Many thanks again!
Three 44s