One other interesting side note. I did a pellet count of the RST shell and counted 326 pellets, which is a bit above the nominal 307 count for 7/8 oz of 7.5s. Interestingly, the shot weighed .875 oz. This would seem to suggest high-antimony shot, presumably?

I just picked up a pair of used Brown & Sharpe dial calipers on FleaBay, and should have an answer to that question soon.

Thanks for the suggestions.

Such a long, long time to be gone, and a short time to be there.