The Truth about Rifle cant and leveling your reticle.

Joined
Dec 28, 2015
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489
The purpose of this post is hopefully to shed light on some myths about rifle cant and help potential long range hunters set up their rifles with confidence.

A while back a friend asked me take a look at his rifle as he was having difficulty making accurate long range shots from an otherwise very accurate rifle. The rifle itself was capable of .5 inch groups out to 200 yards but he was really struggling to connect at longer distances.

I stared with watching him shoot and shooting his rifle myself. Sure enough as soon as I started shooting his rifle I noticed the the installed bubble level appeared to me to be incorrectly leveled to his reticle. I inquired as to who or how he installed the bubble level. He informed me he had done it by using a level on top of the turret cap and had leveled the rifle action the the scope.

I won’t mention the brand of scope to keep things objective here but I’ll say it’s a well respected and widely used “popular” brand and model of rifle scope.

I took the rifle back to my shop and properly leveled the bubble level using the technique described below. It should be worth noting that the top of the turret was 3/4 of a bubble off of being level with the reticle. This caused me concern that the scope would track vertically correctly. I advised my buddy to run the scope through a tall target test to insure proper tracking after I leveled the bubble. The scope failed its tracking test and was ultimately sent back for a replacement which he immediately sold and upgraded.

During the course of problem solving his rifle the conversation of rifle cant came about. After properly installing his bubble level I asked him to shoulder the rifle for an off hand shot and close his eyes. I then adjusted the scope within the scope rings so that the scope and reticle were level when it was shouldered. He was initially upset because he’d taken great time to level the rifle action to the scope and this ended up causing him great concern and he believed his rifle would no longer by accurate at longer ranges.

I explained the mechanics and physics behind my madness and assured him as long as the bubble was level when he fired the rifle his point of impact would not be affected by the rifles cant. He simply couldn’t wrap this idea around his head and so we went to the range and I I showed him what I demonstrated here in the second video.

I won’t go into detail explaining in the thread you can watch the video for that explanation. The fact of the matter is rifle cant is insignificant as long as a properly installed bubble level present.

I put together the first video with hopes of helping folks properly install bubble levels. The vid had over 45,000 views and the sheer number of hate response emails and messages I received advising me I was incorrect about rifle cant was mind boggling. I still receive at least one email a week accosting me mentioning that rifle cant is insignificant. The second video was developed in response to all the “non-believers”!!!

It’s important to understand that rifle cant is only insignificant if a properly installed bubble level is present. Otherwise, yes rifle cant is very significant and will affect POI

I hope this clears some rifle cant myths and helps future or present long range shooters!

Cheers!
Dan

DIY Rifle Scope Leveling the Easy Way: Flashlight Method - YouTube

Canting your rifle. The truth: its not important - YouTube

Here is a video a friend of mine put together explaining the same thing more or less. He actually purposely cants the reticle in relation the the bubble level to account for spin drift!! Now that’s some bubble gum for you to chew on!! This way he doesn’t have to account for spin drift in his long range calculations and dope. I simply rely on my Sig Kilo 2400 for that!

Installing a level on a rifle scope for long range shooting/hunting, and advanced tips. - YouTube

1,390 yards!
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idahoman

FNG
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May 7, 2018
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Spokane
Thanks for the post, I have leveled many scopes with a level on the action and on the scope turret... won't be doing that again!
 

2five7

WKR
Joined
Jul 15, 2017
Messages
657
Great post! I usually try and explain it like this, if the scope is level with the action, you can rotate the gun 90 degrees and use the windage dial for elevation. The barrel is round, so it doesn't care if you rotate it.
 

Fatcamp

WKR
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May 31, 2017
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Sodak
That's pretty cool.

I use a long accurate level on top of the front scope ring with the cap removed. Once I get that set I install the scope being very careful not to move anything. Then draw a level line(side to side) on the wall in front of the rifle. Adjust the scope reticle to be parallel to that level line. Tighten rings to spec, being careful not to move anything.

This has been working for me and leaves me confident that my rifle is level to my reticle. Granted, I'm a short range shooter and don't use a bubble level, but out to 600 yards it has been working for us.

My poor AR doesn't even have a scope right now. :(
 
Joined
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Just to clarify I thought I heard you quickly mention in the first video you need to put a horizontal offset into your ballistic calculator for the distance between centerline of reticle and bore right?
 

weaver

WKR
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Feb 25, 2012
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While I agree with the general concept, wouldn't the horizontal impact of the bullet differ slightly at various ranges due to the reticle and bore not being on the same vertical plane?

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OP
danmayland
Joined
Dec 28, 2015
Messages
489
Just to clarify I thought I heard you quickly mention in the first video you need to put a horizontal offset into your ballistic calculator for the distance between centerline of reticle and bore right?

Yes and no. I usually only enter the vertical offset distance between the centerline of the bore and the reticle. I may have slipped and said horizontal but it’s the vertical distance. This is referred to as “sight height” some programs like Shooter app and Applied ballistics will allow you to input “sight offset” which is the horizontal offset. You certainly can and it’s not a bad idea if your shooting a rifle with significant cant. Usually the horizontal offset is pretty minimal but if your shooting at more than a 5-8 degree can’t it’s not a bad idea to enter it. I’ve never experimented to see how much it actually effects POI. I did measure the horizontal and vertical offset and inputted them into my Sig Kilo 2400 dope solution for the second video.


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OP
danmayland
Joined
Dec 28, 2015
Messages
489
While I agree with the general concept, wouldn't the horizontal impact of the bullet differ slightly at various ranges due to the reticle and bore not being on the same vertical plane?

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Not generally as long as the horizontal offset it calculated in the ballistic solution.


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4ester

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Nov 2, 2014
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Steep and Deep
If your scope Reticle and your turret travel are not perfectly aligned this way of mounting could cause you issues. If you use the Reticle for holdover it will function properly, but if you dial using your turret it may or may not work.

The turret travel and your bubble level must be in exactly the same plane.


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mod700

Lil-Rokslider
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Mar 2, 2016
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Magalia Ca.
Enjoyed the video,... but the line your using is a "plumb line", hence a plumb bob works, it's vertical, a level line is horizontal... just proper terminology,.. minor crap to some, but as a builder it's a quirk. Hadn't seen this method before, but like it!
Mike
 

timberbuck

Lil-Rokslider
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Mar 31, 2018
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Utah
Its good to align the bubble level to the reticle yes. I like to level the rifle and at the same time align the horizontal crosshair to a level checked horizontal line on a wall or tree in my backyard. I then mount and secure the bubble level to match the leveled reticle. As stated this works perfect for hold over reticles but if you are going to twist turrets you still need to do a ladder test to make sure your turrets track true.

Another problem that can surface is if the receivers drilled an tapped mounting threads are not top dead center over the bore or if they are different from each other (left or right from TDC) from front to back. REM 700 action as an example.

Because of all these variables it is obvious that one needs to shoot the rifle at all distances and check.
 
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