That's not the fault of the Powerbelt copper hollow-point. That's not a performance issue with the bullet itself either. Powerbelts were designed prior to 3-pellet use in muzzleloaders. 120-150 grains was never Powerbelt-intended due to the integrity of the plastic cup/base. Many folks using 110-120 grains with Powerbelts load the cup with Bore Butter to substantially reduce blowby & maintain accuracy.
Also... depends on the rifle bore diameter too! Knight Rifles are overbore.... not a good choice for Powerbelts in those rifles unless you slow the bullet down first. Using 348 & 405 gr Powerbelts in Knights seems to work best.
As I said, I don't like a bullet with limitations and cost like that. Just a opinion. I have only shot one deer with the 150gr load. But dozens with 95gr combos in the past. Its not that I like to push the envelope. Just like the option of better speeds if I want.
slamfire, please reread my post, I said it shot ok with low powder loads.