Remington Express PT Bullets

I've been doing a lot of searching around and came across these bullets. They're Polymer Tipped 275 Grain saboted bullets designed for .50 cal muzzleloaders. They come already installed in the sabots like some other ML bullets. 275 grain seems to be the heaviest they make. Hell, I didn't even know Remington made ML bullets.

So has anyone tried these? And if so, what were your results?