There are lots of published loads that are simply bad recipes. Many couple undersized wads with large capacity hulls. For example the Remington and old Winchester compression formed hulls work best with wads with a smaller diameter (Remington, Winchester/Claybuster). The larger capacity hulls like Federal, Cheddite/Herter's, Fiocchi, and non-compression formed Winchesters (which are Cheddite hulls) work best with larger diameter wads like the Gualandi/SG16, Z16 (B&P), and Cheddite wads.
If you post your load I can pretty much tell you what's going on.
