Leveling scope reticles

[savage shooter]

Originally Posted by DaleJ

Savage Shooter
Save your teaching "skills" for something you know. You would get more benifit eating your crayons.

Sir, you have a very poor understanding of the concepts presented here. I had hoped you would gain an understanding of the topic through my illustrations. I'm sorry you decided to be offensive instead.

It's a very simple concept. If the reticle is canted from the rifle then the bore will not be directly below the reticle when it is levelled against the target. If the bullet leaves the bore from a different point (left to right) than the line drawn from where the scope is pointing, then of course the bullet and line of sight can only possibly meet at one distance. They cannot possibly align at any other distance. It is impossible.

It requires a certain amount of spatial visualization to understand this concept. Some people are capable of it, others are not.

As they say: "some people, you just can't reach".

I recommend you read the link that I posted for you earlier and Good Luck to you, sir.

[purgatory.sv]

I am crossed eyed so I will always be challenged. I do have corrective lenses.



Sorry for the derail.

[jzz30tt]

Originally Posted by DaleJ

Savage Shooter
Save your teaching "skills" for something you know. You would get more benifit eating your crayons.

At one point in everyone's life, you realize that the only common denominator in a number of similar arguments is you...

[savage shooter]

Originally Posted by MK2750

I am truly surprised you don't understand this. The bore and line of sight are not running parallel. They are angled towards each other. The diagram is correct and the bullet will fall left and low if the rifle is canted as shown.

Exactly. This is a very simple concept to understand. If the bore isn't directly below the line of sight then the are two lines traveling on different angles which intersect at only a single distance and will be off at all other distances. Additionally, scope adjustments will not track correctly at any distance. It is an impossibility.

I now truly understand why spatial visualization is weighed somewhat heavily in I.Q. tests.


There are people who are incapable of understanding calculus or trig and will argue it wrong from lack of understanding. That doesn't make it wrong, to those who do understand, it simply means that the other person is apparently not capable of that level of understanding. It's sad but not worth much further note.

[nekred]

To answer the question get out from behind the keyboards and experiment!....

Play, shoot, have fun and maybe learn something more than theoretical....

[jzz30tt]

I'll apologize in advance for the image but this is something that is proven by simple trig and physics. IF the scope were perfectly in line with the bore (somehow) things would remain the same however they are on different planes, the scope sitting a distance above the bore. This introduces parallax and error in the bullet path vs the sight picture, especially noticed at longer distances.

[savage shooter]

^^^^ Uh well, yes but that's not the issue. A scope that is directly above the bore will still track correctly.

The issue is when the bore is either to the left or right of the scope. This is what happens when you have a canted scope reticle (relative to the bore).

Picture an older rifle with a side mounted scope. There is no question that the scope sits beside the barrel, not on top of it.

If both the scope and the bore were pointing perfectly straight and barrel was, say, 1" to the left of the scope, then the bullet would impact exactly 1" to the left of where you are aiming the scope. To fix this, we adjust the scope so that the bullet hits where the scope is aiming.

So, due to this adjustment, your are pointing the barrel slightly inwards towards the point of aim to make it hit where you are looking through the scope.

Because the bullet is travelling inwards towards the line of sight, the two lines will only intersect at one point. That point would likely be your zero distance. Any closer and the bullet will not have reached the same line and will still be "outside" the line of sight. Any further and the bullet will continue on its slight left to right trajectory and will be on the other side of the line of sight.

Simple to understand with a side mounted scope, right?

So, now we have only to understand that a canted reticle is the same as a side mounted scope. If the reticle is not level with the bore and is instead "twisted" inside the rings when you level the reticle against the target you are twisting the rifle to do so. When you twist the rifle, the barrel moves out to the side. Try it. Now you have your bore sitting beside your scope, not underneath it and you run into all the same problems as you do with a side mounted scope which is not above the bore.

The zero will only be correct and one distance. The point of impact will hit to one side before that distance, and to the other side after that distance.

Further, adjusting the scope left will not move the point of impact left. It will move it mostly left along with some vertical adjustment too because there is not only vertical parallax but also horizontal parallax too.

This effect is VERY easily noticed in the field when shooting at distance.

[Percher]

I picked up one of these gizmo's today, checked the level of the scope to my rifle and it was smack dab on. No guess work setting up my next scope. I find it's easier to level the reticle looking through the objective end of the scope from the muzzle of the rifle.

http://www.chuckhawks.com/segway_reticle_leveler.htm

[savage shooter]

I have used the wheeler level kits. I didn't find the cheap one did a very good job. The better one with the clamp that locks onto your barrel is the better one. Always verify afterward that the vertical hair in the reticle points directly at the center of the bore. When using the more expensive tool, I find that it always does.

[6.5 shooter]

Originally Posted by gitrdun

Well I think that I do MK2750. But seeing the diagrams that are posted, we may be arguing about two different issues. The diagrams imply to me anyhow that the line of sight thru the scope isn't parallel to the barrel bore. The scope is mounted crooked in other words. The scenario that I'm on about has the scope's line of sight in perfect alignment to the barrel bore, BUT the scope is slightly twisted CW or CCW within the rings which result in the crosshairs being slanted or "canted" when the shooter naturally shoulders the rifle.

My Rem700 is just that kind of beast. I can use the Wheeler levels to level the crosshairs to the receiver as many times as I want. When I should that rifle, the crosshairs are slanted to one side. Now, I'm not about to chop the stock or get shoulder surgery to make up for it, I simply twist the scope so that the crosshairs are level when I shoulder the rifle. No other gun fits me that way, but somehow, this one does.

The problem with Remington fire arms is that the feed rails inside the mag are not level. Same with most Mauser actions

If you level by using the top of the receiver by using your scope base, because Rems receivers are round. Then square the rifle and attach a bubble to the barrel, then mount your scope, using the bubble that is on the barrel, the cant will go away

[6.5x47 lapua]

Originally Posted by savage shooter

THE BORE!



....and even with the canted rifle, the sight has been mounted so that it is directly above the bore when the shooter holds the rifle at a cant. Thus, the bore is NOT canted to the sight for that shooter.

how do you level anything to something that's round? what are you leveling from?the real answer of course is you are leveling to the action which may or may not be even square to itself,let alone be even remotely close to square ? to the stock which is responsible for tracking which is far more important than anything.it is really very simple.amazingly enough british snipers made kills in excess of 1000m with sidemount scopes as did the germans.the real question no matter how your scope is mounted is can you duplicate your form for multiple shots and maintain a level SIGHT PICTURE...

[6.5 shooter]

Originally Posted by savage shooter

^^^^ Uh well, yes but that's not the issue. A scope that is directly above the bore will still track correctly.

The issue is when the bore is either to the left or right of the scope. This is what happens when you have a canted scope reticle (relative to the bore).

Picture an older rifle with a side mounted scope. There is no question that the scope sits beside the barrel, not on top of it.

If both the scope and the bore were pointing perfectly straight and barrel was, say, 1" to the left of the scope, then the bullet would impact exactly 1" to the left of where you are aiming the scope. To fix this, we adjust the scope so that the bullet hits where the scope is aiming.

So, due to this adjustment, your are pointing the barrel slightly inwards towards the point of aim to make it hit where you are looking through the scope.

Because the bullet is travelling inwards towards the line of sight, the two lines will only intersect at one point. That point would likely be your zero distance. Any closer and the bullet will not have reached the same line and will still be "outside" the line of sight. Any further and the bullet will continue on its slight left to right trajectory and will be on the other side of the line of sight.

Simple to understand with a side mounted scope, right?

So, now we have only to understand that a canted reticle is the same as a side mounted scope. If the reticle is not level with the bore and is instead "twisted" inside the rings when you level the reticle against the target you are twisting the rifle to do so. When you twist the rifle, the barrel moves out to the side. Try it. Now you have your bore sitting beside your scope, not underneath it and you run into all the same problems as you do with a side mounted scope which is not above the bore.

The zero will only be correct and one distance. The point of impact will hit to one side before that distance, and to the other side after that distance.

Further, adjusting the scope left will not move the point of impact left. It will move it mostly left along with some vertical adjustment too because there is not only vertical parallax but also horizontal parallax too.

This effect is VERY easily noticed in the field when shooting at distance.

You sir are correct !

Most if not all scopes are nearly impossible to center on a rifle due manly to crooked holes drilled into the receiver. But having said that I try my best to align my reticule to the bore. Then as I twist my point of aim hopefully the bullet will impact near the center line. There is a bit of "crabbing affect" especially with lower end scopes, which most people don't think about.

[savage shooter]

^^ Mmm... well the scope sits in a set of round rings. Leveling it does not pose any kind of problem. Simply make sure the vertical hair of the reticle is pointing down directly to the center of the bore.

You're describing having difficulty in aligning the scope straight with the barrel due to incorrectly machined or drilled receivers. This is common and can be alleviated with some judicious lapping and the use of alignment bars.

[DaleJ]

Savage Shooter

What happens to scope squaring when long shots require a 40 MOA tapered base? If you align scope reticle square to receiver you've only leveled it sideways. The tapered base puts a forward cant on scope. Look at the picture posted by MK and forget about the left canted second scope image, look at the scope that's square. Concentrate only on the square scope. Now imagine that square scope on a canted rifle. Vertical crosshair might be shifted left a mm or two but the scope when square to the target will track. Up is up and left is left. In an afternoon of F-class shooting I might shoot 600, 700, 800, and 900 meters. With a canted scope the MOA adjustments as indicated by hits on target do not correlate to scope turret markings. With the scope square to the target they do. I skip the trouble of trying to mount scope square to receiver, by doing the final scope level tweaking with the rifle in its intended position for shooting either from a bipod or a pedestal. Just for giggles I checked a dozen of my rifles with a goofy reticle level, all except one were very close to level. The one that was out is an RPA Quadlock chambered 6.5-284, which by the way is the best shooter I have.

[twofifty]

Originally Posted by savage shooter

Too bad he's wrong. What he said is only correct for a fixed point. Anything closer or further and it doesn't work.

Good read from the reference provided above.
The math and geometry certainly prove your point.

At the distances at which I shoot (300 yds or less) the matter is kind of moot, which takes nothing away from the value of the intellectual exercise. It's been a good discussion.

I have made every effort to make sure my reticles and rifle muzzles are plumb to each other. I am also aware that consistent shooting form & stance matters, but find it hard to eliminate all cant in the field. I find that trees can help provide a good reference.

[myrand]

i have a theorie that still need to be tested but i am pretty confident that it would work. been wanting to try for a year, just didnt took time to do it.

on a 3'x3' target, perfectly leveled crosshair, always aimm at the crosshair in line with target
at 200M
5shot grouping center
-6moa elevation, 5 shot grouping
return to zero then, +6moa, 5 shot grouping

top grouping should tell wich side the scope is canting, assuming the elevation only moves the elevation.

i guess with grouping bigger than 1" it could get hard to interpret
i would do that on a good rest with sandbags and every aid possible to remove as much shooter mistake as possible

[savage shooter]

What happens to scope squaring when long shots require a 40 MOA tapered base? If you align scope reticle square to receiver you've only leveled it sideways.

Yes, exactly. The reticle should be leveled to the bore (not the receiver) so that there is no left to right parallax. There is already a verticle parallax and it's of no concern. When you adjust the reticle on the scope to zero your rifle, you're already causing the barrel to be angled up. This is why the bullet travels in an upward trajector, reaches its peak, then begins to descend; crossing the line of sight twice. Angling the scope is of no consequence. It simply puts the barrel at an even greater angle upwards allowing for longer shots.

The vertical parallax is okay and expected. It doesn't matter if you exaggerate it with a 40 MOA rail. Because of gravity there will always be a variance in the point of impact on the vertical axis at different distances.

The point is that there must be NO horizontal parallax. The bore must rest directly below the reticle to prevent left to right change of impact at various distances. This is also necessary to ensure that the rifle will actually track left to right or up and down properly.

Also, from what you said above, I get the impression you are thinking of leveling the scope along the length of the receiver. That is not what is being discussed AT ALL.

on a 3'x3' target, perfectly leveled crosshair, always aimm at the crosshair in line with target
at 200M
5shot grouping center
-6moa elevation, 5 shot grouping
return to zero then, +6moa, 5 shot grouping

top grouping should tell wich side the scope is canting, assuming the elevation only moves the elevation.

Yes, exactly. This is easy to see at the range. If Dale isn't seeing it, his reticle must be pretty damn close to being directly over the bore.

[DaleJ]

Originally Posted by savage shooter

Yes, exactly. The reticle should be leveled to the bore (not the receiver) so that there is no left to right parallax. There is already a verticle parallax and it's of no concern. When you adjust the reticle on the scope to zero your rifle, you're already causing the barrel to be angled up. This is why the bullet travels in an upward trajector, reaches its peak, then begins to descend; crossing the line of sight twice. Angling the scope is of no consequence. It simply puts the barrel at an even greater angle upwards allowing for longer shots.

The vertical parallax is okay and expected. It doesn't matter if you exaggerate it with a 40 MOA rail. Because of gravity there will always be a variance in the point of impact on the vertical axis at different distances.

The point is that there must be NO horizontal parallax. The bore must rest directly below the reticle to prevent left to right change of impact at various distances. This is also necessary to ensure that the rifle will actually track left to right or up and down properly.

Also, from what you said above, I get the impression you are thinking of leveling the scope along the length of the receiver. That is not what is being discussed AT ALL.



Yes, exactly. This is easy to see at the range. If Dale isn't seeing it, his reticle must be pretty damn close to being directly over the bore.

You would need a 1000 yd vacuum chamber to prove your point. My point is every long range shot goes through some bumpy air on its way to target and when moving back and forth between different ranges the windage must be adjusted to compensate for wind, wind direction, bullet drift and time of flight. Bullet trajectory is easily calculated, drift, mirage, wind and wind direction effect on bullets is taught only by the school of hard knocks. In my opinion canted cross-hairs are a problem. Square to target offset cross-hairs are not. My targets don't shoot back and I get two pokes to get on target.

[Duramaximos]

I found this explanation logical:
http://www.youtube.com/watch?v=wgTv4WBsBrA
He goes into some extra detail, but very informative imo.
No affiliation with the author.

[savage shooter]

Dale, again the windage and elevation adjustments done on the turrets will not track properly on the x or y axis of the target unless your bore is directly under the scope's reticle. It sounds like yours are. Even a small 3 degree difference won't be noticable with all of the other variables in play in the real world. some people have their scopes canted by 15-20 percent and that can be a big problem particularly at the ranges that you shoot.

Based on what you've experienced, it's clear that your scopes are quite level to the bore, as you've also indicated.

[6.5x47 lapua]

Originally Posted by DaleJ

You would need a 1000 yd vacuum chamber to prove your point. My point is every long range shot goes through some bumpy air on its way to target and when moving back and forth between different ranges the windage must be adjusted to compensate for wind, wind direction, bullet drift and time of flight. Bullet trajectory is easily calculated, drift, mirage, wind and wind direction effect on bullets is taught only by the school of hard knocks. In my opinion canted cross-hairs are a problem. Square to target offset cross-hairs are not. My targets don't shoot back and I get two pokes to get on target.

also bullets do not fly in a straight line.more like a curve ball.it all seems right in math world but real world shooting requires setting the crosshairs to gravity with the natural stock position you are going to shoot the rifle in all the time.there is no other way.if you find yourself CANTING from this position then you are sorely in need of a bubble level attached to the side of your scope to help remedy that.

[DaleJ]

Originally Posted by savage shooter

Dale, again the windage and elevation adjustments done on the turrets will not track properly on the x or y axis of the target unless your bore is directly under the scope's reticle. It sounds like yours are. Even a small 3 degree difference won't be noticable with all of the other variables in play in the real world. some people have their scopes canted by 15-20 percent and that can be a big problem particularly at the ranges that you shoot.

Based on what you've experienced, it's clear that your scopes are quite level to the bore, as you've also indicated.

Your point is interesting but wrong. If scope is level to target it is square and level horizontally with bore, it cannot be anything else. It can be offset from bore to allow a right hand shooter to sight with left eye. The scope will be fine and the shooter will do well with it if his plot card has been prepared for his set up. The sight adjustments will be exactly the same as the scope mounted square on receiver. When squaring cross-hairs to a cylindrical bore, square is square, both ways. Scopes will track as they should either above or beside bore if they are square to target.

[SkytopBrewster]

Are we talking offset or canted, two different things. No issues with scope being offset, or canted vertically (ie a 20moa rail), a horizontal cant would cause problems.

[SkytopBrewster]

Originally Posted by savage shooter

Please excuse the quality of this. I simply used the school supplies on hand that belong to my young son. I believe he would be perfectly capable of understanding this simple geometry exercise.

As you can see, if the reticle is not level with the bore and you cant the rifle to be level with the target, then the bore most not be directly under the reticle. You can see from the second picture the result of this. The bullet will impact to one side or other of the point of aim at any other distance than the one that is zeroed. Aditionally, the scope will not track correctly and any other distance.


upload


pc screenshot

After studying this picture I can clearly see that a canted scope held square to the target would be no different than an offset scope (Such as the old Nagants of WWII), that was mounted "square and level" contradicting my last post. Thanks to 6.5x47L and Savage shooter and Dale J. PS, I just eyeballed the last couple scopes I mounted.

[savage shooter]

Originally Posted by DaleJ

Your point is interesting but wrong. If scope is level to target it is square and level horizontally with bore, it cannot be anything else. It can be offset from bore to allow a right hand shooter to sight with left eye. The scope will be fine and the shooter will do well with it if his plot card has been prepared for his set up. The sight adjustments will be exactly the same as the scope mounted square on receiver. When squaring cross-hairs to a cylindrical bore, square is square, both ways. Scopes will track as they should either above or beside bore if they are square to target.

Sigh....I give up.... Sir, if you want to actually gain an understanding here, there is plenty of explanatory material linked in this thread.

[savage shooter]

After studying this picture I can clearly see that a canted scope held square to the target would be no different than an offset scope such as the ones on the old Nagants of WWII.

Yes, exactly! I have explained this exact thing several times even mentioning those old rifles. An offset scope (which is what happens when you level a canted scope to the target) cannot track properly at more than one distance and it cannot maintain the same left to right point of impact at any distance other than the zero distance. It's a simply fact of geometry.

It's not up for debate. It's simple math. Arguing it is like an idiot arguing that calculus is wrong. Just because you're incapable of understanding the concepts, doesn't make them wrong. They are VERY well proven.

People who keep saying things like "but, but, but GRAVITY always pulls down so if the reticle is level to the target (and the ground), then it will always track correctly" simply don't understand the OTHER problem from having an offset scope as a result of a canted reticle.

[TomCanuck]

Originally Posted by savage shooter

Yes, exactly! I have explained this exact thing several times even mentioning those old rifles. An offset scope (which is what happens when you level a canted scope to the target) cannot track properly at more than one distance and it cannot maintain the same left to right point of impact at any distance other than the zero distance. It's a simply fact of geometry.

It's not up for debate. It's simple math. Arguing it is like an idiot arguing that calculus is wrong. Just because you're incapable of understanding the concepts, doesn't make them wrong. They are VERY well proven.

People who keep saying things like "but, but, but GRAVITY always pulls down so if the reticle is level to the target (and the ground), then it will always track correctly" simply don't understand the OTHER problem from having an offset scope as a result of a canted reticle.

With an offset scope, if you sight in so that the POI is the same distance from the point of aim as the amount of offset, then the line of sight and trajectory are parallel so they do not vary with distance to target.

This issue is more academic than real world in my view. A target shooter gets sighters to set his sights. Unless you are hunting gophers, an inch or two to the side won't matter.

[savage shooter]

Originally Posted by TomCanuck

With an offset scope, if you sight in so that the POI is the same distance from the point of aim as the amount of offset, then the line of sight and trajectory are parallel so they do not vary with distance to target.

You cannot possibly be serious. They cannot be parallel if you want to hit what you're aiming at.

They are two lines which intersect and only do so at once distance. Anything before and they have not met yet, anything after and they have already met and are continuing to get farther apart.

It seems that you are actually advocating for hitting beside what you are aiming at. If that's the case and you intend for the lines to actually be parallel then, yes, you can track correctly and hit correctly at varying distances. The problem is that no one does that. People zero their rifles.

Further, people DEFINITELY don't do that with canted scopes because they don't believe their scope is offset.

[TomCanuck]

Originally Posted by savage shooter

It seems that you are actually advocating for hitting beside what you are aiming at. If that's the case and you intend for the lines to actually be parallel then, yes, you can track correctly and hit correctly at varying distances. The problem is that no one does that. People zero their rifles..

That's exactly what I was getting at, and in practice, it's workable if need be.
I would assume no one would have a scope offset more than two inches to the side of the bore, and in terms of practical shooting, that is an acceptable thing. At longer ranges the wind would cause more issue.

I don't advocate canting a rifle, and I understand the issues with both the offset of the scope, and its rotation by doing so.

[savage shooter]

I don't advocate canting a rifle, and I understand the issues with both the offset of the scope, and its rotation by doing so.

Good. It seems many do not.