depth" does not equate to effective ignition penetration depth. One can envision situations where a relatively mild primer with longer flame duration (e.g., RWS-5341) could well generate more primary ignition by penetrating farther into the charge without pulverizing as much propellant. As one can imagine, resolving the issue of overall burning rate increase resulting from pulverization versus overall burning rate increase resulting from increased primary ignition depth would be somewhat difficult!
Testing Primer Plume Penetration: An Epiphany!
After contemplating for many years how one might go about testing how far the primer plume reaches into propellant charge with sufficient energy to directly ignite granules – this author's feeble brain finally kicked in and functioned! Very likely, this occurred because, for the first time, I had an effective inert smokeless propellant simulant in my hands.The test was pure simplicity; Initially, I chose a conventional extruded smokeless propellant with granules of similar size and shape to those in simulant material (VihtaVuori N160, which is a reasonably typical propellant, in terms of deterrent characteristics, etc.). I then fully prepped a batch of once-fired W-W 45-70 cases. I prepared each of those in the following manner: full-length resized, bellmouth expanded (0.455-inch expander), flash hole prepped (K&M), primer pocket prepped (K&M), and inside mouth deburred and polished.