Its an old topic but i hope someone gets notice of it and spreads the news to all 410 users.
My slug load data tested and confirmed regarding their safety from a proffesional reloader (a friend).
10mm FMJ 180 grain Semi Wad Cutter slug/ Fiocchi 410/76 plastic hull/ Fiocchi 615 primer/ Vectan SP3 Powder 18 grains/ slug wad.
About 940fpe muzzle velocity. 5 Shots 2 MOA at 215 yards with a fixed (non magnified) Red Dot from a bench rest position.
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10mm Lead Semi Wad Cutter Slugs 175 grain cast from a lee 410 - 175 mold. Same components except powder. Powder with this