I haven’t discussed my new Accuracy International (AI) rifle, chambered in 6.5 Creedmoor, too much yet.  (Unless you have been listening to our “We Like Shooting” Podcast, you probably haven’t heard anything about it.)  While I have been waiting for my custom 6XC rifle to be built, I came across a deal on a used AI that I could not pass up, and I had to take the deal!  This meant that I needed a scope. This rifle is going to be my fun, tactical, long-range gun that I won’t mind getting beat up when I’m playing hard.  AI rifles are extremely rugged and known for accuracy and reliability, and with a few specialized tools, changing my own barrels has proven to be fun and easy!  (More on that later.)  But it’s not all roses, along with all that rugged reliability comes a bit more weight than I would prefer in a rifle I’ll be lugging around all the time, so when I started picking components for this gun, weight savings were at the top of my list. For starters I chose a Leupold Mark 6 3-18x for my optic, it is lightweight (only 23 ounces) compact, front focal plane (good for the type of shooting I plan to do), and I love the TMR reticle.  I’ve had some dealings with Leupold in the past that always turned out good so this scope seemed like a no brainer based on my needs.

The first time out with my new rifle and scope out, we didn’t have a chronograph with us, so after zeroing at 100yds, we walked out shots on some known distance targets and made notes of the necessary elevation required.  Using this data I was able to extrapolate the velocity of my hand loads and enter the data into my ballistic calculator.  Using the published G1 BC of the 142gn sierra I was shooting and my newly acquired velocity I began running into some inaccuracies as the distances increased which happens from time to time, but normally not to the extent I was experiencing.  I had a few variables that were hard to account for in just one day of shooting;

  1. New rifle
  2. New scope
  3. Hand loads

The rifle wasn’t a big deal as it functioned perfectly the entire day, so I suspected the loads or the scope.

We hadn’t had a chance to check the Leupold scope tracking before the first time I shot it because it had arrived via a rush order from CS Tactical (Thanks Mike!) on one of my trips to Indiana. I was only going to be in town for a few days, and wanted to shoot my AI and use my Leupold while I was in town. I mounted the scope with Nightforce aluminium rings (more weight savings) that evening, and the next morning we were shooting!

Here is a video demonstration of the test:

We normally always take the time to accurately test the tracking of our scopes for several reasons:

Screen Shot 2013-11-14 at 8.29.15 PM

Following is how we set up our test:

  1. Secure the scope to a stable, level surface.
  2. Measure from the objective lens of the scope out 300 feet (100 yards) with a metal tape measure. (Tape measures this long made out of other material can stretch and throw you measurement off).
  3. Mount a of 4’x8‘piece of plywood.  We built a stand to assist in mounting the board. Place this plywood at exactly 300 feet.
  4. Once the board is standing, use a 4 foot level and make a perfectly level horizontal line very close to the top of the board.  This is your zero mil line.
  5. Measure down exactly18” and make another perfectly level horizontal line, this is your 5 mil line. (At 100 yards, one mil is equal to 3.6 inches and 3.6 times 5 equal 18 inches.)
  6. Repeat step 5. to create 10 mil and 15 mil horizontal lines. (Add additional lines as desired, 20 mil, etc.)
  7. Find the center of the board, and then make a perfectly plumb vertical line down the center of the board, crossing all horizontal lines previously made.
  8. Measure exactly 18” to the left of center, and make another perfectly plumb vertical line, this is your left windage marker.
  9. Repeat step 8. 18” to the right of center. This will be your right windage line.
  10.  Place one inch target stickers on each intersection of the horizontal and vertical lines.

Screen Shot 2013-11-14 at 8.28.47 PM

Once you have the test set up, dial your scope to your rifle 100 yard zero. Ensure the center is precisely on the zero mil target dot at the center-top of your board (magnification is your friend here). Adjust and secure the rifle and ratchet straps as required so it will not move for the remainder of the test.

At this point, dial the elevation turret to 5 mil, and verify the center of the reticle is on the 5 mil target dot indicated on the board. If it is not, note the difference.  Continue by:

  • Dialing 10 mil, note discrepancies
  • Dialing 15 mil, note discrepancies
  • (And continue in 5mil increments if desired – just add extra lines on the board.)

Following this test, return to the rifle zero to ensure you are right back where you started. This will ensure the rifle did not move and the scope returns to zero. Do this test several times to ensure the rifle did not move. You are looking for several consistent, repeatable results.

To check the wind, the test is the same as above, only you dial the wind turret to 5 mil (right and left) and back to zero at each elevation. Note any error discovered.

This test takes a little effort, and a lot of care to set it up properly, but it will give you peace of mind if you take the time to do it.  You will know that your scope is properly aligned, the accuracy of your turrets, validate your ballistic calculator values, and verify your scope returns to zero. I know that most companies probably have an acceptable tolerance of error they factor in, and those values are probably small enough that a human couldn’t shoot the difference. Still, there is a chance that if you do this test, you will find that your scope has a large enough error that it does matter.  This is what happened with my Leupold Mark 6.  When we put it through this test, we discovered that it was off by a little over .2 mil at 10 mil and it was off by .45 mil at 15 mil.  For my 6.5CM, I figured out that I would need to dial 8.3 mil if I were shooting out to 1,000 yards.  The error at this distance could be as much as 7.2”.  Considering there are enough other variables that need to be managed for accuracy, I do not need my scope to add another variable.

We called Leupold and they were really terrific. They listened as we explained the problem, and then agreed that we should send it in.  Leupold does have great customer service. We have already sent it in and Leupold already sent it back (they only kept it for three days!) We will retest it and let you know how it is tracking after the corrections.

Click Here to see all the other scopes we have tested!



11 Replies to “How to test the tracking of a rifle scope”

  1. I cant understand why you dont use 100 meters?1 mil 10 cm,5 mil 50 cm,10 mil 100 cm(1meter) and so on.If you use 3.6 inch at 100 yards you will get a continous error following the tracking as you go along.1 mil at 100 yards is 9.14 cm,thats 3.598425 inches.Multiply this by 5 and you get 17.9921 inches at 5 mils and at 10 mils 35.598425 inches.You will get an error no matter how accurate your scope is tracking with this method.

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