Re: 30-06 velocity question
If you click "Print" on the Hodgdon data the summary page shows the test barrel length. As I recall, the 30-06 used a 24" tube.
The 30-06 has huge potential with longer barrels and heavy bullets, I'm sure you'll get something worthwhile for dropping Antelope in the 20" tube but it isn't really optimal.
To make the best of that 20" tube and the lighter bullets you should try something like H335 or a similar burn rate powder. Fast powder, light bullets will net you the best results. With shorter barrels you're going to be looking for something that can get the most out of a given charge weight, which means you need to burn all of it first.