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Scope center and alignment to the barrel

Ok the scope centering to the action is critical at long range!! The best way is to lap the rings, place the scope in the saddles after cleaning the git free. Next is to level the gun as best that you can, with the two lug action is pretty simple. Locate off the flats of the lugs with a piece that you know is flat, like a small machinist rule and level, sighting thru the scope at a plumb bob. This will get you pretty close. Take the rifle to the range, sight it in to shoot your scopes recommended shortest distance of focus at first. Then at 100 yards you will need a target that is 6 foot tall and a plumb bob hanging in front of the target. Shoot one shot at the center of the target, while keeping the vertical cross hair on the bullet hole, and the plumb bob string. Shoot the second shoot about an inch from the bottom of the target. Now here is where you are going to see the plumb of the vertical line, track the turret knob up (10MOA) keeping the crosshairs on the first and second shoots. Shoot once go up 10 more and shoot another, you will do this till you reach you most MOA you will be shooting. NOTE targets may need to be taller than 6 foot. You will find that the adjustment may be needed. If it does then hang a plumb bob over the target be sure not to move this target till this is finished, clamp the rifle in a sight vice. Line the vertical crosshair up with the bullet holes this is you rifle true level. loosen the ring screws not bumping the rifle around, line the crosshairs with the plumb bob tighten the screws and retest the steps to recheck. DONT SHOOT THE STRING. Scope centering tools are for short range 22lr.
 
Most important thing is that when you are actually firing the gun, your scope is aligned perfectly with gravity. Any cant in the position of the scope will cause a parabolic sideways arc of the bullet causing you to miss low right or low left.

You want a bubble level on the scope to match up perfectly with the erector travel of the reticle. The reticle should match up with this too if all the manufacturing was done right, but it's the erector travel being plum that affects the shot. What needs to happen is that your crosshairs with dialed elevation need to be centered directly vertical above the imaginary point where your crosshairs would be at your 100 yard zero.

Getting the rifle perfectly centered under the scope is less important, as long as the scope remains level. If you shoot with a slightly canted rifle but a level scope, you are just dealing with a lateral offset of the scope over the bore and that might only be an inch or two of lateral displacement at 1000 yards... far less than the effect of canting your scope. For something like a tactical field gun, it's okay to set the rifle in a natural/comfortable position for how it fits on your shoulder and then put a level scope on top of it. For a competition gun you'd want both to be perfectly aligned.

The tall target test you describe is a great way to confirm that your recticle is aligned properly with reticle travel. I recently ran across another method that doesn't require any rounds to be fired, I thought it was pretty clever....

Take two "V" blocks so that the V's are perfectly aligned to each other. Spin the scope in the V, looking through it at a target (with parallax adjusted), making turret adjustments until the reticle center does not move on your target. This is the optical center of the scope.

Adjust the aim of the V blocks to be at a specific point on your target surface, and make sure they are secure and won't move. On your target, make a plumb vertical line that goes through your point of aim. Now, adjust the scope 10 mils (25 MOA, whatever). Rotate your scope in the V block until the crosshairs line up on the vertical plumb line. This is the position that has the elevation turret travel perfectly vertical and plumb. You can then attach the bubble level to the scope.


Now if everything is perfect then your reticle will also be aligned with the vertical line on your target, matching up with your erector travel. If they don't match then you have a canted reticle and might consider sending the scope back to the manufacturer.
 

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