Anti-Cant: Level the Rifle
December 21, 2017
As an instructor of long-range shooting, I have noticed several issues that tend to resurface with each class. One is the problem of a shooter canting his rifle.
Most people will argue that their rifle is not canted, when in reality it is, so the immediate task is to determine whether the reticle is indeed canted. First, purchase a level and properly mount it. Once you have placed a level on your gun and you're at the range, place the reticle on target. Level the reticle to your eye, then check the level for cant to see how well you did. If you were on a flat shooting platform and on a flat range, I would expect that most shooters would do pretty well. However, I've seen more than one shooter surprised at the amount of cant present on a rifle when he felt level at the time.
The first step to correct this problem is to buy a good level for your rifle. There is a large selection of levels available. Some are fairly cheap, while others are rather expensive. Be careful, as some of the models are so nonsensitive that you can cant the level nearly three degrees before the bubble moves. However, I now believe that even a bad level is better than none at all.
Most ranges will have the individual shooting from berm to berm. These berms at each yard line are man-made and fairly flat and level. Also, the trees in the distance behind where we are shooting help us align our reticle with the world. Because we often shoot in flat areas where getting level isn't an issue, it's very confusing when we do find ourselves somewhere where it is hard to determine if we are level. When our rifle is out and we're looking through the reticle, it usually means we're already on the hunt, and then it's too late to figure out if we're canting our scopes.
With an abundance of levels on the market, you need to do a little research before making your purchase. Some of the models available are (in alphabetical order):
Accuracy 1st (accuracy1st.com)
Deros Level Grouse
US Optics (usoptics.com)
Some have unique features such as swivel mounts, covers to protect the vial, top mounts or rail mounts. There are even adjustable features for leveling the bubble while on the rifle and degree markings of cant lines that indicate if you are at 21/2, 5, 71/2 or 10 degrees.
Any anti-cant device is better than none, but some are definitely better than others. There are a lot of differences in these models. Some mount on the scope, and some mount to the rail.
Once a level is purchased, mount it. The best way to mount a level is to place a colored string and a plumb bob downrange a short distance. It will help if it's not too close, as the string will be blurred because of the inability of the scope to focus at extremely short distances. I'd suggest placing the string and bob between 50 and 100 meters.
Using a bench rest or the prone position, level the scope's vertical stadia to the string. Use colored string to make it easier to see. When you have the vertical stadia aligned perfectly, adjust the anti-cant device to read level. This calibrates the device to your reticle.
If you have a normal-style bubble with a line on each side of it to indicate when the device is level, I suggest adjusting the anti-cant device to where the edge of the bubble is touching one of the lines. This makes it easier to identify when you are exactly level.
Now consider whether you need to make the scope level with the gun. This is something I get asked about in class every week. The real truth is that a lot of competitive shooters will shoot with a cant between the vertical stadia and the vertical line of the rifle stock. I've seen some of my students spend a lot of money on all kinds of levels that they place all over the rifle and scope. There is nothing wrong with this, but it isn't necessary. You can quickly mount a scope and get it extremely close to level just by using your eye. First, mount the scope as normal, then — once the correct eye relief is adjusted for — pull your eye away from the scope and make the vertical stadia line bisect the buttplate of the stock. After this is done, you can decide if you'd like to have the reticle straight with the rifle's stock line or if you prefer to slightly cant your reticle.
If you do decide to cant your reticle, you'll need to make sure the reticle is still level with your anti-cant device. I would strongly advise against extreme canting of your reticle from the centerline of your stock. A small cant may allow a more comfortable ergonomic feel between your rifle and shoulder, but too much can destroy the relationship between the centerline axis of your scope and the centerline axis of the bore. This creates external ballistics issues. The most important thing to remember is that you must level the reticle for every shot.
I've watched men mistakenly assume that the shot they just missed off the edge of their target was due to some unseen or ill-measured effects of the wind. Deep down, we all realize that we are not as good at calling wind as we would like to be. Winds will always be the nemesis of the long-range shooter. I tell my students that I truly believe every five-mph change equates to a 10 percent loss in first-round-hit capabilities. This applies to targets between 600 to 800 meters with a target size of 12 to 16 inches.
I like to train in an area where winds average 17 mph. The terrain features and the cap-rocks that cover the training area also enhance the effects of the wind. Most often, when the shooter barely misses the intended target, he believes that he just narrowly misjudged the wind call. However, a well-trained spotter can (and often does) correct the shooter's cant, and then the shooter can hit the next shot with the exact same wind call.
To show you the math behind shooting a scope that's canted, the following examples show the difference in where the bullet will hit with the cant as opposed to where it would have hit without the cant.
If the scope is canted by only 2½ degrees, the bullet will impact .05 mils for every 100 meters in the direction of the cant.
'¢ A 400-meter shot would have a .2-mil shift (approx. three inches)
'¢ A 600-meter shot would have a .3-mil shift (approx. seven inches)
'¢ An 800-meter shot would have a .4-mil shift (approx. 12 inches)
If the scope is canted five degrees, the bullet will impact .1 mil for every 100 meters in the direction of the cant.
'¢ A 400-meter shot would have a .4-mil shift (approx. six inches)
'¢ A 600-meter shot would have a .6-mil shift (approx. 14 inches)
'¢ An 800-meter shot would have a .8-mil shift (approx. 25 inches)
Most of the time, the shooter will try to level the gun by adjusting the bipod. Even though this would be a proper correction, the shooter may not have the time required for it. By understanding where the bullet will impact due to the cant of the rifle, the shooter can adjust his hold and get the desired impact by holding off the target to account for the impact shift. This takes some training.
Most shooters would think that they could see 2½ degrees and for sure five degrees of cant. I would normally agree, until you place a shooter on a downslope and have him shoot at a target on a hillside with the horizon running anywhere but level. This describes all three of the areas in which I take my students for training.
I can understand how shooters on flat ranges without terrain features may not have noticed the problem of not being able to see when their scope was slightly canted. I was fortunate early in my life in that I was running around with a scoped rifle on a daily basis. I had trained my eye to a point that I didn't think I needed help from a level. I know now that I was wrong. Today I want a level on every scope I have.
So which device should you use? There are many levels available, and most are very affordable. If you really compare anti-cant devices, you will find that some are a lot more accurate than others. Something you may want to consider is where the bubble is placed in relationship to your vision.
The most convenient anti-cant devices allow you to transpose the image of the level onto your reticle. For example, you see the level with your nonshooting eye while you are looking through the scope with your shooting eye. You do this by focusing on the level with your nonshooting eye, then changing focus to your shooting eye, which will drag the image of the level onto the reticle. With a little practice you'll be able to pull the image of the level on demand.
What you don't want to do is lift your head out of the scope to check your level. This is an unnecessary and time-consuming movement. Still, even doing that is much better than not having a level at all. If you can't afford a level, I would suggest that you try looking over the top of the scope and level the top turret to the horizon. This will help solve the canting problem until you can afford to purchase a level.
Take time to learn the differences in the products you're looking into. Pick a quality level, and better enjoy your time on the range and improve your long-range shooting.