I had been getting really bad leading in 9mm shooting Hi-tek coated heavy-for-caliber bullets (trying to work up a soft-shooting USPSA load). Didn't matter what pistol they were fired from, the leading was pretty atrocious all the way down the barrel. Finally figured out last night that the cases were swaging the bullets down to .354 or .3545. Was getting less leading with bullets cast in a different mold, a Lee 356-125-2R, but was still getting some. Come to find out, they were being swaged down, too.
So I got on here, did some reading, and that's where my question comes in: am I understanding correctly that I need to buy either a Lee Universal Expanding die and a NOE expander plug or a Lyman M-die? Does the expanding plug expand the brass down to the bullet seating depth so the case doesn't swage the bullets down?