One thing I am learning pretty quickly though is just simply picking something based on where on the burn rate chart it falls is not correct. A faster burning powder might and often does give pitiful velocity results out of shorter barrels.

There is a category of 'other' that is the real X factor. I think the burn rate matters (for sure), but there are other more important characteristics involved. Basically my current hypothesis is if you can get high velocity from published data as well as being higher on the burn rate chart, then you have a good candidate.

For example with a 75 grain bullet H4895 is listed as giving 2,907 fps out of a 24" test barrel on Hodgon's website. It is also #94 on the burn rate chart.

For relative comparison CFE223 is #111 on the chart and TAC is #92. Between those two on their website the velocities are respectively 2820 for TAC and 2876 for CFE223 using the same barrel length.

My real world testing though with a short 10.5" barrel gave me drastically different results. I got around 130+ fps better velocity out of TAC (in the short barrel) with everything else being constant.

I don't know what that 'X factor' is for powders that generates more velocity for a given grain weight bullet, but that 'x factor' PLUS the burn rate matters I think.