The .504" lead slug I show for using in 12ga sabots is
one cast for using in .500" cases like my 499HE, by
sizing it after casting. Tried it at the .504" diameter and
it works in the sabot also. So it does double duty,
unsized 12ga sabot, sized and lubed in .500" use.

Some like short cases in big calibers, and have put up
various ideas. First picture is 12ga brass cases, two
2" long and other 2.25". Cases made by shortening
our cases we made by putting rims on bmg brass.
These can be used in Savage 210 and feed from mag
box. Can use 2.5" Magtech brass shortened so case
and protruding slug will be 2.7" overall and feed from
magazines of Savage & Mossy bolt guns. With 2.25" case
you can get 600gr to 1800 at least.Ed