HalfaDouble,
I am somewhat familiar with shaped charges, having completed basic class and practical training in demolitions with the US Army Corps of engineers, which is nowhere near as extensive as my friends in EOD (Explosive Ordnance Disposal). The reasons I am unsure that a "shaped charge effect", rather than something else caused the ringing are: a shaped charge requires a high explosive( smokeless powder is a flammable solid); the charge( explosive) itself is shaped with a void( generally cone shaped); the effect is linear( along the axis of the void); for a "shaped charge effect" to produce the pressure to dent the steel, it should leave some signs on the brass case, if not cut it through. While I have never seen "ringing" happen, enough people have, that I can believe something causes it. It seems, therefore, that if the actual cause can be determined, it can be avoided to avoid "ringing" while gaining the advantages of fillers. This would require much more research than I am able to do. It is known that Kynoch uses foam filler in their NIB loads intended for old rifles, so they must have done extensive research into fillers, maybe you can obtain a copy and share it here.
Mike
