*Laser Bore Sighting*
By: Fireman
22 May 2011

I purchased a laser bore sight that fits 7.62 series rifles like the M-1A. It will work just as well in a .243 Winchester sporting rifle. The laser will certainly put your first shot on the paper, but there is a random effect that I wanted to overcome.

The laser comes with printing on it to caution you not to close the bolt and never to dry fire the rifle with the pointer in the chamber because it could destroy the laser. I decided to take advantage of the fact that there is a mark already on the laser.

I put the laser in the chamber with the print up and recorded where the light was in relation to the crosshairs. Don't adjust yet. Then I loaded the laser with the print straight down and recorded where the light was in relation to the laser.

Next was printing on the laser to the right and printing to the left. The four points thus recorded made a rectangular box. I drew lines corner to corner and adjusted the crosshairs to that intersection.

It worked. My first shot at 25 yards was dead center in a one inch square. I repeated this short experiment and it worked every time. Then I repeated the experiment with the iron sights on the same rifle. It works with iron sights too.

This procedure will only work with chamber laser sighters. It won't work with optical bore sighters that use muzzle spuds.

I drew from experience in other fields to develop this procedure. When a surveyor determines the bearing between two points he "turns up the angle" four times. That way he gets two pairs of angles. The locus of those points is the exact angle between the points.

In 1998 we had a huge ice storm in Maine. Commercial radio towers collapsed from the weight of accumulated ice. To get the exact locations for the FCC permit to rebuild I used the locus 10 north/south latitude readings on a GPS and 10 east/west readings. That satisfied the FCC. It would have taken weeks to survey from a USGS marker to the tower due to all the downed trees and the distances involved. There were not many hand held GPS units around in 1998.

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