That is a .40-cal 200-gr inside the sized-down .45 ACP brass sabot. Maybe slit the .45 ACP case with a hacksaw in hopes of changing a non-discarding into a discarding sabot. R&D continues, just for yucks.
Ron aka "Rip" for Riflecrank Internationale Permanente NRA Life Benefactor and Beneficiary .458 Winchester Magnum, Magnanimous in Victory THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.