Well of course they wouldn't let a 500NE go by if stamped 24ga,
as a 24ga case wouldn't fit the chamber, and the barrel bore is not 24ga size.
But our 24ga has a 24ga chamber and bore, and fits 24ga cases you can reload
and loaded factory 24ga rounds. BPI and Precision Reloading sell 24ga plastic and
brass cases the go in the chamber. We just made a stronger brass case that
can be loaded heavier. Rocky Mtn Cart makes brass cases that can be
loaded heavier in 24ga and all shotgun calbers. Either are legal cases.
Your 500NE loaded at factory about 2000 fps, but modern non balloon head cases
they can be loaded a third faster if you want. No difference in concept.
Factory hotrod sabot loads for 12 and 20 ga have over 50% more energy than
old foster slug loads, legal for both them and us to do it...
Plastic shotgun cases take a certain pressure, magtech brass takes 50% more,
our cases and Rocky Mtn cases take twice the pressure as plastic.
You can find some aluminum shotgun cases that take 50-70% more than plastic.
All legal. BPI and others sell sabots, slugs and stuff that gets reloaded to twice
the energy of factory loads, all legal........