The reduction in cal. gives better sectioal density so more penatration. I shoot a bore this year with a 250gr Shock Wave the blue tip bonded 45 cal in a 50 cal sabot whent in the left front shoulder and out the right ham just behind the hip the hog was only a bit over 100 pounds but it dropped him like a rock the load I was using chrony at 2080 fps.
No copper fouling
I have been shooting sabots since they first came out I clean with boiling water and citrus or simple green soap and have not had any plastic problem.
I have not needed a second shot so I dont know how to answer that. Lee