For a scope mounted ~1½" above the bore, the bullet's trajectory will cross the line of sight near 25yds, so the closer you can bore sight to 25yds, the closer you'll be with the actual shot. This is just a general rule, there are too many variables for it to be exact, but it will work either with a laser bore sighter or just looking thru the bore. The problem with looking thru the bore and adjusting the scope is the rifle moves when you touch the scope, a laser bore sighter doesn't, the laser point always stays in the same position relative to the sight picture. I love my laser bore sighter and I've been a dyed in the wool look-down-the-bore kinda guy for 40+ yrs!!!
Reminds me of my hunting partner's experience once.....he had his scope base screws break and the scope fell off when shooting at a buck at the first shot.....the buck just stands there looking at him at about 50yds....he takes a couple more shots just looking down the barrel....still no dead buck....he walks over to a nearby stump, places the rifle on the stump, pulls the bolt, looks thru the bore lining up on the buck's chest, carefully loads the rifle and shoots the buck!!!! That one should go in the Guiness book!!!!
Tim