Steve, if you're thinking of using this information to "push the limits", there's a much more reliable, safer (relatively) and fairly inexpensive way to do it than eyeballs and micrometers.
RSI Pressure Trace
Pushing the limits of pressure is not very productive. As an example, using a 150gr Hornady A-Max in 30-06 with a 24" barrel, QuickLoad gives 3,162fps at 73,300psi and 2,988fps at 59,900psi with a max load of H380.
In other words, you get a 5% velocity increase for a 22% pressure increase.
If you're just wondering in case you run into these things in load work up, I wouldn't be concerned about reaching these numbers. If you stay in book limits and do what you're supposed to do, you'll know there's trouble before you get these kinds of pressures.
A chrongraph to check velocity against expectations would go a long ways too.