I found a picture of 28ga Rossi Circuit Judge. Barrel is
smooth bore , could be little heavier barrel, but it will do
ok with the new plastic case Brenneke slugs,
260 gr at 1450 fps..Could do 2000 in a little longer
brass case from RMC.

28ga is a 550" bore in a rifled bore.
24ga is about .585 same bore as my 585, and
most all 577/585 stuff. The 28ga chamber with minimum work
would fire my shorter 585 with a switch barrel 585 bore.
And still work with 28ga with 28ga barrel put on.
Difference is the case thickness with the 28ga case
being nearly the same OD as my 585 drawn, stronger
brass cases.

The Brenneke slug has along locked on base and seal,
connected by long post, that you can see inside
the case in picture and pictured on the box
Quite a long tail so to speak for
good smooth bore work.This is a great step forward
for 28ga slugs, as most reloading slug stuff was only
100 grain balls or other super light slug designs...ED