The boresighter the OP is considering shows a price of $17-$60. I can zero a rifle bolt rifle at 100 yards with 3 shots and be within 2" of a 50 yard bull on the first shot without one. I can zero any other rifle in no more than 4 shots. That is not opinion, that is fact. I have better things to spend my money on. Anyone using 1/2 a box of ammo to get their rifles zeroed is doing something wrong and using one of these tools isn't going to make things better.
Even with the tools you still have to adjust your sights, the only thing any of them claim to do is get your 1st shot on paper. That is no trick without one.