Some recent news has made this topic interesting again. It appears that these BPI sabots can get the 500gr bullets to 2550fps with the right wadding and seals.
Ed Hubel posted this, here is what he said:
Ed Hubel posted this, here is what he said:
One of our testers, Bret in MN, got the BPI Sabot with
500gr Hornady .500 slug up to the good speed listed
on BPI"s loading sheet, using shotgun powders. I could
get them there with my loads using much larger amounts
of rifle powders. He tested 3.5" Federal plastic cases in
his Savage 210 with 3.5" chamber and the 28" heavy barrel
he put on. With 50gr of Longshot(max load for all modern
guns) he got 2550 fps, with 500gr in sabot. He use two
BPGS gas seals fitted together over the powder, then
a FS12 Flexseal wad, then a 1/4" cork wad, then the sabot.
He also did one with one BPGS and two Flexseals and had
200 fps less.He had tried other combinations seals/wads
and with same amount of powder and got lower yet.