More 12gs slug/sabot info-- About discarding sabots.
Most factories making sabot slugs make them relatively light,
300 to 350 grains, and that is why they are on average
more accurate than what guys try to reload with heavier
slugs in the sabots. Reason is light slugs don't damage
the sabot, while they are trying for high velocity.
Example is picture of Hornady SST sabot and it only has
a one way plastic seal over powder, and a hard
rubber cushion inside the sabot under the 300gr jkt
spitzer style slug. Many 12ga hunters say these are
the most accurate.

Another slug idea is a blunt nose jacketed slug of
675gr I made from one of RG's hollow point jkt slugs.
I cut part of jacket off of the front and swaged
it over to make blunt nose. These are for the guys
trying to make short loaded brass case rounds
in 2.5" brass and 2.62" brass to be no more than
2.75" overall to work in certain guns. it is
on left, 2nd pic. And gets good velocity with just
good BPGS seals under it and slower powder.
On right is US-S sabot with discarding petals, locked
on base we tried in short brass case, and can't, due
to length of sabot get in enough powder to get
the higher velocity with heavy 700gr US-S slug, the
guys want to get.....ED