That trend with Powerbelts may hold true for most powders. There seems to be a "window" of powder charge with the PB's where, if you are below that window you don't get sufficient upset - and you are above it the stem gets deformed and doesn't release the skirt consistently. All that might have been required to cure the problem with the Scout is to up the powder charge enough to get the bullet to flow into the lands and grooves. How much Clear Shot were you using?