Generally speaking...............Knight's are not known for their ability to shoot PowerBelts (due to their shallow rifling I think). I have shot & hunted with the 348gr Aero-tipped PowerBelts and found the accuracy good enough for hunting (consistent 2" groups at 100yds) with 90gr of 2fg 777 powder. I have heard lots of conflicting reports as to their impact on game. Personally, I shot a wild boar through the shoulder with the above load and the bullet cut straight thru and never expanded any - others have reported excellent expansion on game....................So they seem kinda like a box of chocolates...."You never know what you're gonna get".
There are 2 things to watch for with the Powerbelts:
1) Don't try to push them too fast if you want to maintain accuracy
2) Lube the little post that holds on the sabot cup before you shoot them.............if that cup sticks to the bullet (which it will with hoter powder charges), accuracy gets BAD quickly.
If you just don't want (or can't by law) use sabot bullets, you might try the No Excuses lubed conical bullets. They have performed very well out of my Knight USAK so far (accuracy wise) and they pack quite a punch too without the need for high powder charges. If you want to try sabots, try the 300gr Hornady XTP Mags or SSTs....................both shoot very well out of these short barreled Knights.