I have an original 14 bore on my ticket that i shoot, very much a lower quality piece but a good shooter.

I started with the "equal volume loads" but i really didn't get good performance, it could well have been my poor skill but i started adjusting my loads after hearing an old rhyme

"less powder more lead,
Shoots far, kills dead"
"More powder less lead
Kicks hard, wide spread"

A properly sized wad makes all the difference.