In my admittedly limited but honestly practical DG experience, if you want to replicate dangerous game moving towards you for rifle practice, then you should build a cart with solid wooden wheels with no suspension and have it bouncing over a rough gravel road, and have the silhouette of the animal's head mounted on a coil spring so that it can sway, move, and swing all over the place as it's coming at you.

The "shooting schools" that I've seen on TV where the target moves at a nice, steady, and even pace along a cable are about as real as reality TV.

Just my 2 cents.