It's the difference between "Let's eat, Grandma!" and "Let's eat Grandma!"...
Bazoo is the OP.
Quickload is an internal ballistics solver program that can take load specifics (cartridge, bullet, powder, etc) and predict chamber pressure and velocity among other things. Runs on Windows. kinda spendy. Not a substitute for data generated with proper pressure testing equipment, but informative none the less...
Quickload, Bazoo!