Dave, I think your twist is a little slow for sabotted bullets, unless you use real short ones. I would try the Power Belt type and perhaps some of the big Buffalo Bullets or Hornady Great Plains type also.

I have always found plastic sabots a real pain to load, particularly after firing a shot or two, but the Power Belts load easily. They can be very accurate, but some people have not been able to get them to shoot accurately in some guns.