Piece Boresighter Kit will ensure that your rifle is accurately zeroed when
you’re testing out a new rifle and scope combination. This Boresighter fits
snugly in the rifle barrel to eliminate any “play” that can result in an
inaccurate boresighting adjustment and poor shooting accuracy.
How a boresighter works
Insert stud into boresighter and insert other end into barrel. Align internal
grid. Scope is now pre-zeored.
Caliber (Cal.) is a system of measurement for the internal bore
diameter of a rifled-barreled firearm (rifle or pistol) based on the decimal
part of an inch (.22 Cal) or in millimeters (9mm). American caliber designations
refer to the distance from land to land, not groove to groove.