I tested both the standard and magnum loadings a couple of years ago, using my 12-gauge Remington 870, w/18.5" cylinder choke barrel and rifle sights. At 100 yards, accuracy was considerably worse than standard Foster slugs.
I tried chonographing velocity but the sabot halves wiped out two of my skyscreens. (I knew I was risking equipment damage, but figured, "eh, what the heck -- I might get lucky.")
Shot some through two plates of heavy sheet metal, which was meant to simulate a car door. It easily penetrated without deflection on angled shots.
The slugs are about .45 caliber in diameter. I can't remember the weight. The cartridge roughly turns a shotgun into a .45-70.
Neat concept but they didn't work for me.