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Understanding Parallax Parallax and a Clear Image
How often do you hear at the range – “It must be my Scope”

Today’s Benchrest Quality Scopes are some of the best ever made. More often than not when a scope is deemed bad by a shooter it is usually just a ‘loose screw or nut’ which is not a part of or connected in anyway to the scope.

One of the advantages of these ‘loose screws’ is that I have been able to buy some great scopes cheap! One seller was such a basket case that I did him a favor in stealing his scope. How can that be you ask? Well after an hour working with this shooter and thoroughly testing his scope his shooting was deteriorating at such an alarming rate that I was concerned if he would even be able to shoot in the next days match. So after buying his ‘bad scope’ and screwing on a brand new scope his scores started improving and I had saved the day. Of course after the match the next day he told me his brand new scope was now bad!

Above you will see some links to some papers written by Leopold on the setting the focus and parallax. So if you think you might have a bad scope do some reading there and insure you understand what they are saying! With the quality of today’s bags and rests a “return to battery” or very close is almost the norm. Set up your equipment and hang a LEVEL target. Check that your scope bases and rings are tight (do not over tighten). Check that your rest is steady, level and your crosshairs are level on the target. So the next step is to sit down and put some rounds down range and look closely when you return to battery is your Point of Aim (POA) returning. If not confirm that it is not your equipment that is preventing return to battery! Forgot POI it does not matter if you even hit the target! If your POA is returning then your scope is probably ok – but lets run one more test - Tracking. The problem with this test is that you have to fix the dropped shots and flyers that made you think you had a scope problem before checking its tracking. If you want to "Shoot the Box" use something like an RBA or IR 50/50 target.
Sight in for an X.
Now put your crosshairs on one corner of the box surrounding the bull. (Top Left) Holding your rifle steady in this position click you scope down and right to the 10‘X’.  Now take a couple of shoots (POA 10X).
Your POI should group in the Bottom Right corner.
Now Lets put our Crosshairs on the Bottom Left corner and click Right to the bottom Right corner. Now take a couple of shoots (POA 10X).
Your POI should group in that bottom left corner. You can now repeat the above for other corners.
Understand that with these large changes in POA you will get some lateral or vertical deviation in tracking. But 1/4 or even a 1/2 inch is not good enough reason to scrap a scope.


Doug Dec 08