John,
You are correct, a little harder lead and smaller hole in the hollowpoint, or a thicker copper jacket and I am sure the bullet would be able to take a hotter powder charge without blowing up. But, I think that most folks would loose allot of accuracy by doing that too.

Look at some of the pictures of recovered PBs on this thread and others. At least the ones that aren't all blown to bitsbecause theywere shot w/ milder powder charges. The thing that one notices is that the bullet itself has very deep rifling marks. Many people think that the little plastic skirt is all that seals the bullet. I don't think this is entirely the case. I think that the bullet is so soft, try and squish one with a pair of pliars, that the bullet actually deforms due to the acceleration and obturates to seal the bore. The leadin PBshas about the consistancy of cold play doh. The skirt helps initially, but the bullet acutally does the seal and bite into the lands and grooves providing very good accuracy and performance when shot with proper powder charges. I also think this is why the heavier the bullet, the better the performance.

The only difference between a powerbelt and a maxi ball is the pretty copper color and the plastic hoola hoop, and about ten times the price.

Hank