Experimenting for fellows trying to get speed with heavier sabot slugs than
the lightweight saboted 4-500 gr kind of slugs, in 2 5/8" length brass
cases for where length is limited..

Using 770 gr saboted slugs with locked on base, by US-S.
Thes are long saboted slugs due being brass and locked on base.
Real hard to do with these due to lack of powder space for the RE17
and IMR 4759-4227 that I like to use. With 770 gr and 60gr 4759 got 1450 fps.
With 75gr Re17 about 1350 fps. Both of these all case will hold under sabot.

For contrast using full bore 730 gr Dixie with just seals under it, much more
powder room, with 95gr 4759 getting 1800 plus and 130 gr RE17 1700 fps.
I went to faster powder, my slowest shotgun powder, Alliant steel, to try to get
speed like full bore slugs get.

These listed are max loads before brass cases expanded to much and started
sticking, due to sharp expansion step, where the base goes to the side with a
real small inside radius on this particular RMC brass case.
47gr Steel,and 770 gr slug 1400 fps.

So I tried the 570 gr US-S with 53gr Steel,and got 1700 fps. Same slug with
65gr 4759 got 1650. You can put in more Steel but cases stick.
And cases expanded that way are hard to resize.

The first 3" brass I got years ago, same problem with
a sharp step expanding above the base. So when I had 3.5" brass made
I had them do a long inside radius from base to the sides. These with extra
room for powder and cushion are much less problem. I think where you have
to use shorter cases, you can use plastic, as a 3" plastic is 2 5/8"
when crimped and will do the same and only be 20 cents or so new.Ed