Ok so I messed up BIG at the start by assuming the two of Lee's .410 molds were for a shotgun when in fact another commenter here fortunately brought to my attention that those molds were actually for a 41 Magnum
So after the commenter's other suggestion for looking into the Svarog and Lyman .410 shotgun sabot slug mold, I found the Svarog on Ebay but ablsolutely no results on Ebay or net for a Lyman .410 sabot slug mold. So I've been relentlessly trying to find the specific load data for this Svarog .410 sabot slug but still absolutely no results, which blows my mind after seeing how many thousands of these molds have been sold over the years.
Here's just a couple listings I found on the Svarog sabot slug mold on Ebay:
https://www.ebay.com/itm/Sabot-Slug-...w/273419906620
https://www.ebay.com/itm/410-Gauge-S...e/133457410488
So my wife's shotgun is a Mossberg 500 .410ga Made In USA that just bought her brand new last Fall, and its barrel has stamped into it "Chambered For 2 1/2 And 3 Inch Shells. 410 Bore - 24 Inch Full Choke"
I know to use W209 primers like I do with my 12ga Lee 7/8oz KeyDrive slug loads as well as for my 20ga Lyman's 350gr Sabot slug loads, and so I mainly need to know what powder and wads to use and what shot cards if any are needed. I will also be using either the Remington and/or Winchester 3" hulls whereby using the fold crimp like works perfectly for my 12ga and 20ga slug loads.
I've also contacted the sellers of the Svarog mold on Ebay but seeing they are in Russia, I can only hope they understand and speak good English so there's no communication farts that screw up the understanding between us like it notoriously often does when we've tried to ask questions with sellers from Asian countries