Another 12ga sabot idea, first picture is a 570 gr USS slug,
with Powder Cup seal from BPI, locked to USS discarding sabot
section. This shortens column so that we can get more of the
slower powders in we use, in shorter 2.75" cases. With slower
powders, they get to peak pressure a little easier
so that the cushion usually between seal and sabot/slugs
isn't needed. This locked on seal will aid in smoothbore
accuracy and it will work of course in rifled barrels.
This sabot has a peg on the back that locks it in original
setup to the green USS cushion base/seal, and we just pried
it apart and drilled tight hole to match in the Powder Cup
seal, and forced it on for a locked fit..
Slug is .629" diameter.

Next picture is 3 sizes of first USS sabot slugs, with
the locked on bases which work good with them. Giving
nearly rifle accurracy in smooth bores.

Here is old time picture of couple of Rodda 4 bores.
Man what nice old guns.

Next picture is a 1.5" Minie ball slug, might work for
close to a one gauge. It is next to older 37mm case which
might fire it also. Maybe a way to make a one gauge of
sorts, if.......I get enough ambition...Ed