I don't suppose there is any way to actually know what's happening in the bore with these under gauge wads unless someone was to build a clear barrel that would withstand the pressures, and use the high speed photography. That would be a "labor of love", though. I can see no financial incentives for going to that expense and trouble, especially given the limited usage/need of these inserts in the first place. They're no more than a curiosity to me. I just have a wondering mind.