How I measure my scope height - Paul Reid
Have you ever had one of those days where your new scope/rifle combo just would not do what your DOPE said it should (assuming all other factors like speed & bullet type are correct in your ballistics calculator).
Every ballistics programs will ask you to enter your scope height. How do you measure it?
My definition of “measuring scope height” is “the distance of the center of your bore to the center of your scope”.
I’ve tried several methods. Ruler, laser pointer, beer can, small cat..... a different result every time (although the cat was pretty close).
Questions: Does measuring your scope height with a ruler or other measuring device take into consideration any MOA that is built into the scope base? I believe my method allows us to eliminate this forgotten variable.
Here are 2 ballistic tables, one with the scope height set at 1.9” and the other at 2.5”.
As you can see, the difference between the two scope heights can cause an error of up to 0.2. That could be a big deal if you are shooting a 2 MOA diamond at 600 yards.
What does it do to your “up close” DOPE?
As you can see, the difference is huge. Does it matter? Answer.....a little.
We have had 6 yards shots in matches, if you dialed 7.8 when it should be 10.4, you’d be close to the target, might even hit the edge but you would not hit absolute center and this could cost you points.
Is this a big deal for shooting PRS matches. Answer = NOPE. If I was not sure of my scope height I would just enter 2.0” and go to the match. I’m sure I would do fine. It will matter if you are shooting loopholes or anything up close but that is maybe 1% of PRS shots.
THE PURPOSE of this article is to help you to measure and eliminate one of the forgotten variables in setting up your precision rifle.
Have you ever had one of those days where your new scope/rifle combo just would not do what your DOPE said it should? YEP, I certainly have. When this happens, we need to eliminate the variables. I start with scope height.
Here’s how I measure my scope height and I believe my method is 100% “real world accurate”.
GO SHOOT YOUR RIFLE AT A CLOSE DISTANCE!
If I can only shoot one distance then I would choose 6 yards. Measure from the target to the CENTER of your scope (this is important and it’s exactly how you would shoot a loophole, to the center of your scope).
Typically, these are the distances I like to shoot at to prove my scope height. 6,7,8,9,10,15,20,25,50 yards. I find though, once I get 6 yards nailed my D.O.P.E. is perfect at all these distances.
HERE IS THE METHOD IS USE
- Measure from the target to the CENTER OF YOUR SCOPE.
- I start shooting with whatever D.O.P.E my ballistics program tells me and then I dial it in until I get and absolute center hit 2 or 3 times.
- I’ll check what my scope has dialed and tweak my scope height in the ballistics program until my D.O.P.E. matches what is dialed on the scope exactly for that distance.
- I’ll move to 10 yards and retest. If I have time, I’ll shoot several distances.
- I’ll make a note in my shooters log of the rifle/action/barrel/rings/scope combo and record the scope height I used and the D.O.P.E. for 6,10 & 20 yards.
Honestly, this method is very liberating. Once you prove your scope height, I believe your D.O.P.E. should be spot on at any close distance.
Here I started on the 3/4” dots at 6 yards with 10.4 dialed. I dialed down to 7.8 MILS and got a center hit.
Then I moved to the 1/2” dots to confirm. When I was satisfied I had it dialed correctly, I went into
Geoballistics and adjusted the scope height down until it read 7.8 MILS at 6 yards.
After I made this adjustment all other distances were perfect.
2nd dot bottom left was my confirmation at 6 yards.
You will notice not all of the shots are dead center. There are some other variables to overcome like “can your scope parallax at these close distances?” and can you really pull a good shot every time you pull the trigger???
Considering that after I confirmed at 6 yards, the following 1/2” dots were shot at 7,8,9,10,12,15,20,25,30 & 50 yards I am “ok” with the results. NOTE! There was no further adjustment to my scope height in Geoballistics, I just dialed the D.O.P.E it gave me for these distances.
So in closing I will note that this info will not make a better shooter, just one that is better advised on the variables that may make you ”pull your hair out”. I had an issue with the D.O.P.E on my 284 about a year ago. It would hit targets at nearly all distances I tried and then not at 750, 900 or 1100......very...bloody....confusing. It was scope height. Once I had tried the methods in this article I realized I had the scope height wrong by 0.5”. Just another variable to consider when things get confusing.
SIDE NOTE: WTF with starting at 6 yards??? Well, I wanted the results to have a practical, real world meaning. 6 yards is this distance from the 1st deck to the ground at Rifles Only (a shot we have had to take a few times).
I hope this info is useful to you.