I have a few Boresighter...One being BSA Optics Boresighter with barrel adapters from 17 Cal to 12 gauge..
Bushnell with an arbor you insert in the barrel..Nice once you get it zeroed in you can put it back in the gun.
Take a recticle reading and scribe on a target just where this particular recticle is set in relation to the bullseye of a target.. mark the target with the bullet type, reload data etc..Next time you want to use this bullet.. Insert the boresighter and change the scope recticle close where you made the image on the test target data you used before..
Then a few Lazer type you stick in the barrel..I has been recently I just found one that has a 17 Cal adapter.
I have boresighted numerous ways..Bolt actions by taking the bolt out and looking down the chamber to the bullseye and adjusting the recticles while the gun is being held in a gun rest of some type..
I never shot a gun after bore sighting and have it hit near the bullseye.. Actually I start off shooting at a target at 25 yards first... I add paper above the target and most times it shoot real high so I do have to move it down 18 inches..
Hopefully people will never have gun boresighted and think they are right on for hunt without fine tuning the scope a bit.
Probably most accurate would be for bolt actions just removing the bolt. However we all don't use bolt actions.
Recently saw one in the Sportsman Den catalog..It attaches to the front of the barrel by a magnet..This probably could be used for most guns..Just place it on the front of the barrel.
