Steve; burn rate charts are notoriously misleading. Powders perform differently in different size cases and at different pressures. Use a burn rate chart as a very rough gauge only.
Another misconception is that shorter bbls. require faster burning powders for best results. Not true. It is true that more of the fast burning powder will be burned, but the best ballistics are from the charges listed as having the maximum ballistics, usually slow powders. For example, a 3" .357 Mag will work fine with Unique or a similar reasonably fast powder, but best ballistics are obtained with H-110 or W-296, slow powders.
Hope this helps, Walt