It could be. It’s the closest thing we have to measuring pressure. Nothing is the same in reloading. Everything is different and has variables. But if a safe pressure in a manual states a given FPS with a certain grain. It may take your rifle 1 grain more powder to achieve them same results or it may take your rifle 1/2 grain less. If you’ve got a loose barrel you won’t have pressures therefore you won’t have the velocities. If you’ve got a tight barrel you’ll have increased pressure and therefore you’ll get an increase in velocity with a lower powder charge

Hope makes sense.
Jeremy Mette

-Shoot Straight... Shoot often-