I have used Powerbelt Platinums in 50 caliber with 150 grains of 777 pellets. They shot accurate, 1.5" at 100 yds, but I think they performed poorly on deer. Yes, they killed them, but fragment and no pass through on small deer. I would not recommend them on elk.
I live in NYS and am not restricted on sabots. Many sabots though are very hard to seat, some even with a clean barrel! That was my reason for going to the Powerbelts in the first place. I am now looking for another bullet. My requirements (not necessarily in order of importance) are 1) good accuracy; 2) work with 150 grains; 3) be able to shoot 3 times before cleaning is required; 4) hold together on game.
I have tried Black Horn 209 and compared it to 777 Pellets. I used 3 bullets with both powders, with 120 grains of 209 and 150 grains (3 pellets) of 777. I discerned no verifiable difference between the 2 powders in terms of bullet seating or ease of cleaning after 3 shots. The gun was grungy when cleaned and both powders required additional "oomph" to seat bullets after the first shot.
Bullets used were a Barnes (tipped, don't remember the exact name), a TC Easy Load sabot and a Hornady easy load. Of the 3, the Hornady loaded the easiest on a dirty barrel, but didn't give the best accuracy. The Barnes was arguably THE best designed bullet; however, the sabots required 2 men and a small boy to seat - even difficult on a clean barrel! The TC was the most accurate with the 777 at 150 grains.
All 6 loads tested were accurate for 150 yard hunting, but when one shoots 2.5" and another is 1.5", there's not much contest there. So, I hunted with the TC for a few years then tried the Powerbelt for a few, killing 3 deer. Now, I plan to try the new Federal belted bullet. Unsure if that would qualify as a sabot or not for CO guys. Its not monolithic, but is one piece....