ORIGINAL: HEAD0001
Bore sighting at 15 to 25 yards will do the job. But the farther you bore sight your rifle, the closer to being on the X will be. I normally try to bore sight between 50 and even out to 100 yards. I takes a couple more minutes, but will save on shots. 100 yards sounds like a long way, but it is not. Your eye will find the center if you trust yourself. Tom.
I agree with Tom.... Boresighting at 100 yds. will give you very accurate results if you TAKE YOU TIME AND USE A SOLID REST. The procedure has been spelled out well enough in the previous posts. Use the bore as a peepsight and the target dead center. Remember to keep the same amount of bore visible as you center the target. Very important!! Adjust your crosshairs to the center of the bull, and constantly re-check your bore picture. You will be amazed at how close you will be if you take your time and re-check sight pictures. (Bore vs. crosshairs). I've done this many, many times, and usually do better than a lot of the laser boresighters.