Scope Reticle Cant – The Disease

Unless you have been shooting more than 600 yards with zero wind – yes, zero wind – you may be infected and not even know it. I sure had the disease for almost four years before discovering that my dope was just not what it used to be.

The saga began when I found a place on my farm to put up a new target at about 620 yards. Although I could score hits, elevation and wind settings just seemed off; not by much, but something felt odd. I made appropriate notes in the data book and moved on.

Several weeks later I placed a new target at 700 yards, set up the dope and fired – no tell-tale ping. Re-adjusted the wind turret and sent another round – again no tell-tale ping. On the third shot I saw dust kick-up low-right. Made the necessary dope corrections and finally heard “ping”. Problem was the elevation was 1.25 MOA higher than my base-line 700 yard dope and wind dope was 2.5 MOA left which was simply not justified by the actual wind. Clearly something was wrong with this picture!

A few days later I went out just after daylight when there was zero wind to again try 700 yards. Used the 700 yard base-line elevation with zero wind and promptly missed low-right. Then I used the earlier dope and heard the familiar “ping”. I thought, “Ok my 100 yard zero has shifted” so I went to the 100 yard target. Guess what, 100 yard zero was good. Welcome to the disease; scope reticle cant!!

Reticle cant is different than rifle cant. If the vertical stadia of the reticle does not coincide with the vertical center line of the rifle bore, the reticle is canted and the scope needs to be rotated inside the rings.

Rifle cant is when the rifle, with the scope, is tilted to the side when firing. Sniper magazine, published in 2011, has an excellent article about cant which states 2.5 degrees of cant will shift the point of impact by 3 inches at 400 meters and by 7 inches at 600 meters.

Back to the problem at hand; how to rotate the scope reticle to line up with the rifle bore center line? This was not an easy problem to solve.

In an ideal situation you can hang a plumb bob on colored string at a distance of 50 plus yards, level the gun and rotate the scope until the vertical stadia is aligned with the string.

In my case, leveling the gun was a big problem because there is not a flat spot anywhere on the gun or the scope. After a long struggle I finally got the gun in a reasonably level position and could see the vertical stadia was tilted to the right about 3/8 of a mil. Loosened the scope rings and rotated to scope.

Now back to the 700 yard firing point to try again. This time the original dope worked and I heard the familiar ‘ping’.

Some of you may say “We all know the vertical stadia must line up with the barrel centerline. What’s new here?” Nothing new at all – except the problem is easily masked in wind calls and range estimations when shooting at the longer distances.

I am really glad I kept everything in my data book so I could refer back when something just did not seem right. Without having kept good data from all the various ranges – Badlands, etc. , I would never have suspected any problem whatsoever. I simply would have just chalked up the experience to wind call errors and/or range estimation errors.

One last point – there is the possibility that all your dope is based on a scope reticle that is slightly canted. As long as the scope stays in this position everything will work just fine; although wind and elevation dope will be different from that of a non-canted reticle. However, dope is unique to every rifle/scope setup, so if it is working for you, leave it alone.

Thanks to our family member Trace Maker for this article!

One Response to “The Disease”

  1. JBoucherMD,

    Had a phenomenal time at Tactical Shotgun. 3 trips to Badlands and never been disappointed. They are going to get sick of me in 2016. Too many good folks, too much good fun, and too much learning all things we all come to learn makes a perfect trifecta. I feel blessed as an Oklahoman to have such an amazing place to train so close. Alright gentleman, I’m bringing my brother from Las Vegas to the next Reactive Destabilization Course. He may be Captain or Lieutenant LEO by then, but I’m still big brother so get us the schedule b/c I need two spots! Couldn’t be happier to be a part of the BL’s family.
    Jeremy Boucher, M.D.