If you don't know the velocity of your round you're just guessing. Fundamentally more important, you're guessing about wind drift as that is a function of time of flight, wind vector(s) and BC. As long as your practice includes 2 uncontrolled variables you will have a fundamentally difficult time - easily eliminated with a relatively cheap chronograph.
David
You still have to shoot at known distances to figure out POI. Doesn't matter how fast your bullet is going if you don't practice at comfortable distances, you wont know where it is going to hit, even with a chronograph.
