I have ~50 load books that don't get used anymore.
I find my start point with Quickload.
I write up a range report with velocities and accuracy.
The co relation between predicted velocity and pressure are very good with bottle necked cartridges not touching the lands.
The prediction is better for jammed into the lands if start pressure is manually moved up from 2,000 psi to 8,000 psi.
The prediction is bad for bulk powder. I got a lot # of surplus bulk IMR4895 that is so fast, the H322 constants entered into the canned Quickload library will match the pressure and velocity results.
The prediction for overloaded straight wall pistol cartridges is very poor. The 1,000,000 psi 2,500 fps never happens. What happens is a big fire ball of unburned powder.
Some bullets in the Quickload library do not have a length entered. One must measure the length of the bullet and enter it manually.
Some powders are not in the Quicklaod library. IMR800X-HiShokr is one that I have. The old guy selling Quickload in the USA, at NECO, says that is becuase that powder varies too much.
I have found that 22-250, 243, 257 Roberts Ackley Improved, 6.5x55mm Swede, 270 Win, 7x57mm Mauser, 308Win, 30-06, and 8x57mm Mauser all have the same case head and all have the same max pressure for long brass life, 62,000 psi.
I could also test 250 Sav, 300 Sav, and 35 Whelen, but I think I already see the pattern, the Mauser case head with large Boxer primer is all the same, despite the difference in SAAMI registered max average pressure.