Andrew, I have always operated under the assumption "burn rate" correlates the charge weight required to achieve a given velocity, i.e.: a larger charge of a slower powder results in the same velocity as a smaller charge of a faster powder. I don't know how Hodgdon calculates "burn rate" nor how closely my concept of burn rate correlates with theirs, but previous editions of their chart agreed with my real world data perfectly. Unfortunately their latest revision places HS6 on the faster side of the other popular 9 major powders which doesn't jive with my concept of burn rate nor my data.
In my mind I group 9 major powders as fast, medium and slow:
Fast (7ish grains for major with a 115):
CFE Pistol
Autocomp
Silhouette
Medium (8ish grains for major with a 115):
HS6
Longshot
Slow (9ish grains for major with a 115):
SP2
3N38
These are just powders I've tested, but don't include: 3N37, N350, AA#5, AA#7, True Blue, etc.
Good thing you don't include 3n37 that stuff will torch a Schumann