My right eye looking through the bore at the target has always been more accurate than any device I've tried. The 1st shot at 50 yards is always within 2-3".
With a lever or any other gun that you cannot see through the bore simply use a larger sheet of paper for the 1st shot, or reduce the range. I'm usually within 1 or 2" of the bull in 3 shots at 100 yards with a bolt rifle. Add 1 more shot for rifles that I cannot see through the bore with. Ammo is expensive, but not that expensive.
If you sight in dozens of rifles a year a boresight tool might pay for it's self in a few years. Or if you own a gunshop and offer free boresighting with a scope purchase I could see buying one. But I cannot see the expense when they save zero shots with a bolt gun, and only 1 shot per sight in with non bolt rifles.
