I'll share with you what I've come up with so far as loads. AA5744 start at 45gr and a 250gr Hornady XTP in the Hornady sabots, the high velocity ones. I've tried the MMP's that everyone else was using and had zero luck with them once velocities got over 2200fps, and these were the ones that MMP had reccommened for the Savage. I've taken the Hornadys and the 250gr XTP to close to 2500fps with 5744, anything more and the sabot would turn itself inside out and who knows where the bullet goes as it missed the 4'x4' cardboard completely. Keep everything in the 2400fps range and my gun will keep 10 shots under 1 1/2" @ 100yds.
Hogdons Lilgun does equally well. Again start about 42gr and work up to 46gr. This load isn't listed in the Savage book because Hogdon is against the Savage as a smokless muzzleloader. Lilgun and 5744 are the only 2 powders I've tried and both are equal in accuracy. When I get the chance, I'll try some other bullets.
The Hornady sabots have been by far the most accurate. Knights and MMP's have been the worse. I can't see any difference between the 250gr and 300gr XTP's as far as accuracy. Another thing to keep in mind, don't let the barrel heat up. This makes the sabot soft. I start to see a difference on the third shot of a 3 shot group. Usually I shoot 2 then wait about 5 min. for the third and so on. Usually get about 10 shot a hour.
Accuracy is just simply outstanding with this gun. I have 32 shots thru this gun since the last cleaning, (and there isn't much cleaning). Last nite I shot 2 shot as fast as I could and they both were with in 1/2" from the last time I shot last week. Our deer season here in Michigan starts tomorrow and I'm using this gun with 48gr 5744 and a 250gr XTP in a Hornady sabot. 3" high at 100 is 3" low at 225. Not too shabby for a blunt pistol bullet. I have also used WW, Federal and CCI 209 primers and can't see no difference in any of them in accuracy.
One last note, when you get your gun, do a good barrel scrubbing with JB or Flitz or USP. Mine was pretty "cruddy" as it came from the factory, almost like they used blackpowder to test fire it. Also remove the ventliner from the breechplug and coat it and the breech plug with never seize. The ventliner only has to be lightly tightened as it tightens itself, sorta like a cars oil filter. Savage says to change the ventliner every 100 shots. I changed mine every 200 and didn't have a problem.