Rifle cant and scope cant.

greg11

greg11

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Reading a bunch of articles about cant, but after a while it just seems as if people online in the various forums start talking in circles.

Hodnett on the Magpul vid made mention of the idea that rifle cant doesn't matter. What does matter is scope cant. I cannot really see this making sense. Does it?

Then I see 16 time National High Power champ Dave Tubb's gun:
http://www.gun-blog.com/2011/08/what-cant.html

My point is this. Hodnett says you can just "eyeball" whether your scope is relatively level to your firearm by making the reticle as close to perpendicular to your weaver base as possible. Is that really good enough?

Also, I'm a little concerned that my Burris Signature rings have my Sightron off the bore axis. It just looks a little off, like the scope body is pointing to the right (at the front). Just a little though. would that have an effect? I'm guessing no, because that's what the knobs are for (correcting misalignment between the optic and the firearm)! Right? Wrong?

This is all blowing my mind.
 
All factors are irrelevant if they are always the the same all the time. If you shoot at a single fixed range at all times, and are able to consistently line your scope up in the exact same way, every time you shoulder the rifle, you have no issues. However, if you change the variables, either the distance to to target or the cant of your scope between shots, it can become and issue. Ultimately, for an all purpose firearm, you want your scope to be directly over the center-line of the bore, and the have the scope perfectly in line with the axis of gravity. This will assure that as you change positions and distances, you mitigate the greatest number of variables and allow for a more consistent shot. Obviously, the greater the magnitude of variables (cant angle, distance to target etc) the greater effect will be present on your shots grouping. Hopefully that helps in some way.
 
The barrel is the part of the rifle that matters when you are shooting, and yes, it does not matter (in theory, as it's a round tube) if it is canted or not. However, once you bolt a scope on it, the mis-alignment possibilities are mind boggling indeed. Luckily, in real life, it isn't that bad. Until you start shooting at real long range the amount of cant really is not going to make much difference, and the internal adjustments on the scope will bring you on target. As you stretch the shooting range, though, those minuscule differences multiply, and then they will matter as you try and stay on target. - dan
 
I'm no meteorologist but agree that you can not cant a round tube :)

That being said, I level my action/receiver using a wheeler level level and make sure my reticle is straight using a string plumb or laser level on the wall. While everything is level I attach my anti-cant device (I use a scope mounted anti-cant) now everything is square, theoretically.
 
For a full free floated barrel, Rfile cant means nothing. If your barrel is bedded and has pressure points, your rifle should to be held "true".

Scope cant is the big "killer" in accuracy though. If your crosshairs aren't level, all sorts of strange things will happen.
 
IMagius said:
Scope cant is the big "killer" in accuracy though. If your crosshairs aren't level, all sorts of strange things will happen.
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Canting the rifle and level crosshairs are two different things.

If you had a simple scope with mildot reticle and turned it 90 degrees clockwise you would still see a perfect mildot reticle. Your windage dial would now become your elevation and vice versa.

If instead your scope was turned 45 degrees clockwise you would now see an "X" and your adjustment dials will be effecting your shot by changing your POI in diagonal increments.

If you canted your rifle 45 degrees counter clockwise your reticle will now be level and will function properly.

The issue that effects accuracy is when you think your crosshairs are level but really your target is just canted. Also, your terrain may not be level but gives you the impression that it is so you cant your rifle to make the sight picture look level. Both situations will affect your shot. They say as little as 5% cant can significantly throw you off.

I believe in anti-cant devices and have them on my rifles.
 
In dealing with rifle cant, what lots of people forget is that you CAN cant a round tube. Because attached to that round tub is a lot of non-round parts. In a perfect world the combination of the recoil lug, shoulder position, etc. all plays a part when it comes to cant. Due to the design of the recoil lug, the effective part of the lug is the bottom portion of it, sticking into the stock, chassis, etc. Since this can not be designed much differently, some energy is transferred down the lug into the stock. Think physics, every action has an opposite reaction. So, when this energy is transferred downwards, the rifle is moved slightly upwards, resulting in some hop and the problem of staying on target after the shot is made. Now when you think about it, if your rifle is canted, this energy is no long transferred in a straight vertical plane, but rather there is a small vector in the horizontal. As your projectile is travelling down the barrel, for a very small unit of time it is affected by this movement in the horizontal plane. After your projectile leaves the barrel it is no longer travelling in a perfect straight line straight ahead of you with movement only in the vertical plane (arc of bullet during travel). Because of this, gravity now has a slightly different effect on the projectile, throwing off your POI.

With that being said, a slight amount of cant at smaller distances (not 1000 yds) won't have much visible effect. But, once you start shooting further, you'll notice. But try it out, cant your rifle and see what happens as you shoot with more and more cant. Your POI will change.

Now, slight cant can adjusted for with your windage/elevation. There is a reason these are adjustable, to adapt to varying situations.


Ideally, no cant is best. Can some cant be dealt with? of course. Is no cant easier to deal with? yes.

Tcon as makes good points about scope cant.
 
Rifle Cant

IF your scope and barrel are not in the same vertical plane, the only concequence will be the offset of the barrel to your reticle, meaning your rifle is now (for example) 0.5 inches off to the right and 0.2 inches higher than where it would have been if it was all square. You cannot cant a tube, as previously mentioned.

Look in a balistical solver like JBM and these values are accounted for. If there is no cant, they are zero, and you need only to put in scope height.

A level reticle is very important however. Think of shooting off a car trunk on a 10 degree slope. Your elevation adjustments would also bring you left or right.





I called BS after whatching that on the Magpul video too but Jacko here explained it. I'm glad I didn't pay for that video though, 99% of the advice they gave was just another promo for very pricy gear.
 
In simple terms, if you mount a scope on a rifle and it is not "square" to the rifle's bore, when you aim the rifle and align the scope with the horizon, you in fact are pulling the rifle's bore out from under the crosshairs. For the hunter, all he has to do is adjust the reticle to his point of impact. The problems of mis-alignment for anyone who chooses or must dial elevation for various distances, the tracking of the scope is in fact away from the original point of impact, depending on whether the scope is canted to the lest of the right. For those interested, and have the time, cant one of your scoped rifles and see what happens, or just roll a sighted rifle to one side or the other and see what happens to your previous zero.
 
Haagen_Dazs said:
You cannot cant a tube, as previously mentioned.
Click to expand...


I was not talking about a tube itself (obviously its round), I was simply talking about the rifle as a whole. The barrel alone does not dictate the accuracy of a rifle. The accuracy of a rifle, however, is dictated by the sum of its components, taking into account their design and functionality together (not including the skills of the shooter). Since the barrel is only a fraction of the whole, the effects of cant on the whole rifle must be taken into account.
 
Okay, how about lateral deviation?
Like This:
lateralr.png


Can your optic's internal adjustment effectively bring that problem under control? If I'm zeroed for 100yds, will my verticle tracking stay on the same plane?

The more I look at my setup, the more I swear the optic is off axis just like pictured above. Just a tad.

But if I zero my windage so that the red optic line and the boreline are the same point at 100 yards, would I just need comeups to move out to 300? Or would I need comeups and some windage?
 
if i understand you correctly... if your scope is not in line with the bore and let’s say you are zeroed at 100 the further out you shoot you will see the misalignment of the scope effectively compounding with added distance it is very important that the scope and bore are in the same plane. the internals cannot fix a cockeyed scope mounting, well the only way it could is if you adjusted your windage to account for the cockeyedness of the scope at all distances you are shooting. the elevation of the scope will be fine though , you will need come up and windage to fix a cockeyed scope.
 
Situation 1: Your scope is crooked laterally, but the reticle and the bore in in the same vertical plane (no scope cant):
A single windage adjustment when zeroing will elliminate this problem. If you refine your drawing so that the black and red line intersect at the rifle (bottom of the drawing), it would resemble what I'm talking about.


Situation 2: Scope cant, in addition to lateral misallignment, causes the picture you drew.
Now that the bore is offset (as drawn) you can see how the further out you go, there is a requirement for additional windage adjustments too keep the bore pointed on the point of aim. Regardless if your lateral allignment is good or off, you will always have this problem if you mount you scope canted (aka your bore is not in the same vertical plane as your reticle). You drew this situation perfectly!

lateralr.png


Basically, if your bore is 0.5 inches off the center of your reticle, your bullet will, theoretically, always impact 0.5 inces to one side (the right in this case). This is regardless of range. Therefore, whether you're shooting at 100 yards or 1000 yards, to correct for this 0.5 inches, you'll need to come 0.5 MOA right at 100 yards, or 0.05 MOA at 1000 yards.
 
The only time you will notice scope cant is at longer ranges with turret scopes as you dial the scope up to hit farther targets if canted you will move to the right or left .
 
DEZ said:
The only time you will notice scope cant is at longer ranges with turret scopes as you dial the scope up to hit farther targets if canted you will move to the right or left .
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Let's be clear that that is the kind of scope cant where your reticle is not plumb to the ground, or true to the horizon.


The other scope cant is done while mounting it to the rifle.
 
You can't cant, if you want to shoot longer ranges. Get the Wheeler Level, Level, Level. Great little tool, cost about $35 bucks. Level your rifle, then level your scope, then move on. Done. You have now eliminated one potential accuracy impediment.

If you are only shooting at 100 yards it's not critical to eliminate cant, one or two degrees won't make a huge difference, once you get to distance it's very important.
 
Haagen_Dazs said:
I called BS after whatching that on the Magpul video too but Jacko here explained it. I'm glad I didn't pay for that video though, 99% of the advice they gave was just another promo for very pricy gear.
Click to expand...

I completely disagree. I think there was more practical advice than commericals.

I improved my shooting position with some of their recommendations.

The way I see it is if I can find something in a video/book that helps me improve then it is worth it. It's the collection of all the tips/techniques in your arsenal that makes you a great shooter or helps you in unique situations.
 
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