Gizo wrote:What is the mirror technique?
I'm not sure how this got into the Bore Sighting story but the "Mirror Technique" is what is used to center your Scope Crosshairs to zero elevation and windage. You place a mirror on the front of your scope (with a good light source) and you will perhaps see two images of the reticle. One is the reticle itself the other is the reflection that will be off center if not zero. You adjust both elevation and windage to get one single image. That's a Zero Setting which is how a brand new scope should come out of the factory. It's a starting point.
Then you "Bore Sight". To me there are two meanings to Bore Sighting. One uses something called a "Bore Sighter" attached to the Muzzle end of your barrel.
The method of Bore Sighting that I use is to put a target out at 100m (perhaps 50m for a .22LR) but no closer. My targets are A4 Page Size taped to a Beer Box sitting on the ground. I put my rifle in my rest on a bench and look through the bore. I center the A4 page in the bore looking from behind say 3-400mm away then look through the scope. I adjust the scope to be perhaps 50mm higher than center then fire a shot. 99% of the time there is a hole in the target. I then reposition the scope crosshairs to the bullet hole and adjust windage / elevation back to the point of initial aim. Second shot should be exactly where point of aim is, if not a fine adjustment for a third confirmation shot.
Two - Three shots to sight in a rifle scope exactly. Then, move target further out to like 2-300m and check point of impact... not when it's blowing a wind gale or wild mirage.
Job done.