Here's three powders in three different cartridges. Velocity was recorded over duplicate chronographs (Oehler 33 & Pact PC2) or triplicate chronographs (Oehler 33 & Pact PC2 & Oehler 35P) run concurrently with each bullet fired.
Tract 1 is Retumbo
in a 7mm Rem Mag with a 168gr Berger VLD. Barrel length = 24 3/8".
Tract 2 is IMR 7828
in a 300 Win Mag with a 210gr Berger VLD. Barrel length = 25 1/2".
Tract 3 is H1000
in a 280 RCBS Improved with a 162gr Hornady Amax. Barrel length = 28".
I know the H1000 speeded up as the temperatures dropped. Don't ask me why. Best I can figure is they've treated the Hodgdon Extreme powders to increase burn rate as temperatures fall. In this case MV increased with this lot of H1000 with decreasing temperatures.
Notice the big differences between the two Hodgdon Extreme powders and IMR 7828.