There is a heck of a difference between loading a tight sabot and loading an over-sized ball, or Minie style projectile. I tried a Hornady FPB which is a copper jacketed "no skirt" Minie style projectile. They looked cool and worth trying. They mic out at .507 at the base. It was "hernia class" hard to load in the T/C. Might be much better in a different gun.
Birch, I tried these quite a bit in both my TC and my Savage. They were a bear to load in either but actually easier in the TC due to the flared muzzle. They were nearly impossible to get into the Savage. FYI...they didn't shoot any better than most sabot/bullet combos I tried. They were "OK" but not great. In case some of you don't know it, PowerBelts are so loose in some guns that if you hang the gun upside down in a stand they suggest you push the bullet back down on the powder. They will actually move off the charge. I got them to shoot pretty good but they performed poorly on deer. After shooting seven whitetails with them I trashed them. They disintegrate on impact. I've never recovered an entire bullet, never had a pass through, and in two cases had the bullet explode on the outer hide and never even penetrate the animal. They're for people too lazy to find a good load or have no idea of what good bullet performance really is.