Originally Posted by lobster
I have an SN 3 from US Optics, yet to mount it. Instructions say to first center the erectors, ok no problem, then says to rotate the scope 360* to make sure reticle is not elipticle,while aiming at 100 yd target, if elipticle, use elevation and windage knobs to bring retical to perfect circle. Is any one familiar w/ this proceedure ? If so could you expand on this some more ?
Centering the erectors/turrets, is a way to get you close to optical center and is typically done by counting clicks from the top of the turret adjustment to the bottom then dividing that number by 2 to get your basic starting point. Do that for elevation and windage and you should be close. Rotating the scope 360* and watching the reticle is their way of fine tuning to a perfect optical center. When you rotate the scope, if you are off center the reticle will appear to move around in an oval in relation to the target until you adjust the turrets and find optical center.
A small cardboard box with weight in the bottom and v cutouts to hold the scope will allow you to turn the scope consistently while looking at the reticle-to-target relationship.
This process is important because it helps you make sure your scope to bore alinement is correct. There are a number of things that can mess up proper alignment like receiver issues, base misalignment caused from improperly drilled holes, crooked bases or rings, etc. knowing the proper starting point is important to making sure you are setup correctly in the end. But keep in mind mounting your scope optically centered is usually only done for traditional shooting at closer ranges which would be on a flat base. Most LR guys end up using a sloped/canted base or rings to ensure their scope works properly at the distances they shoot and to make sure they have enough elevation to shoot LR. If you are going to be using a sloped base your adjustments may change but at least you know where center is so you can adjust things to your desire.
Many shooters like their scope to be optically centered at the distance where most of their shooting is done so for LR range guys that is maybe 600-1000 yards. This is because the scope is optically the best when centered so optical aberrations are limited giving the shooter the best view of the target at the distances that are most critical. Also as a turrets reaches its max adjustment it can begin to lose consistency or change in adjustment per click or stop working all together (especially if say the elevation is close to max and then the windage turret is used). So by using a sloped base or adjustable rings like the Burris signatures you can pretty much set up your scope to run as well as possible and have the least chance for error at the longer shots where the real necessity for accuracy is at.
I really like the Burris signature rings for setting up a scope correctly. They really spoil a guy after using them. They really are the slickest concept I have ever seen. The adjustable inserts allow you to get almost perfect scope to bore alignment and cant (if needed) without using any internal scope adjustment. It is all done with the inserts. Then you know that your scope can be adjusted from its center which gives it the best chance to work as designed. The rings also grip better than many standard rings, leave the scope in a near zero pressure environment (unlike some rings that are misaligned and end up bending the scope when the rings are tightened, and never leave ring marks on your scope. There are more ways to accomplish this but nothing I have seen that is as easy, cheap, and that works so well.