How does using a chrono help dial in your barrel?
If you know the exact velocity that the bullet leaves the barrel, along with the bullet weight and BC, you can plot the trajectory of the bullet. With this information you can adjust the sight so that the bullet will stay within a certain distance of your line of sight. Say for squirrels, a small target, you may want the POI to be no more than 1/2" higher or lower than your line of sight so that you can hold dead on without having to compensate for the trajectory out to the point that it drops 1/2" below line of sight. Just put the + on the target and squeeze.
For centerfire/deer I adjust so that the bullet will never be more than 3" above line of sight, anywhere along it's path and know that I can hold dead on out to the point that it drops 3" below, which is about as far as I'll normally shoot. Beyond that 250 to 300 yard mark you will know how much you need to compensate for additional drop, also from your chrony info. It takes all/most of the guesswork out of the process.
This information will also tell you the distance where the apex of the bullet will be so you know where you will need to set up your sight-in target.