Vertical alignment of Rifle and Scope?

[elkhunter11]

Originally Posted by Dean2

Chuck

Chuck, OI give you credit for sticking to this discussion as long as you did. I sort of bailed a while back. Looks like you, me Cat and a couple of others have finally got through to at least the majority of the people on here. I summarized my posts for ease of reading. These pretty much clarify the issue under discussion being: If the rifle is canted but the scope is plumb to the world, no meaningful POI shift occurs. If you cant the reticle, as little as 5 degrees can cause a miss of a man size silhouette at 600 yards.

To reiterate and summarize my posts -First being Post #11 of this thread

Post 16 still misses the point that when the bore and crosshairs are perfectly parallel, the only way that they can be aligned identically left to right, is if one is perfectly above the other. Amy other orientation results in horizontal offset, and any scope correction to compensate for that results in the crosshairs and bore no longer being parallel left to right. If they aren't parallel left to right,then they can only be perfectly aligned left to right at one point/distance. That is basic geometry, and it can't be changed. The only question is how much angular error is introduced to align the bore and crosshairs left and right. If it is a very tiny amount, it will likely not be noticed, but it still exists, there is no way to cant the rifle without introducing a horizontal offset.

[AndrewM]

Originally Posted by CNP

Not checking the math but I'm happy to see you've come around. 90 cants aren't typical and neither are crosshairs 1" from the centre of the bore. Shouldering someones gun with crosshairs that are not level with the rifle irritates me. I level the rifle in a bed, I then mount the scope level using a plumb bob. I shoulder the rifle...….if the image of the crosshairs is not level I will readjust my hold until the crosshairs are level. Fire away. This is "the" proper way to mount and use a scope. Mounting a scope on a canted rifle is the same as mounting a scope that is not level and will induce deviation as you have illustrated.

What do you want me to use as a cant and a crosshair distance from the bore. If I use 2" crosshair distance and a 5 degree cant you get 0.7" of movement at 1000 yards. That is much less than 0.1MPH of wind. Definitely a lot more variable that matter more. For hunting distances which are probably max around 500 yards that is 0.26" which again is negligible compared to every other factor.

By readjusting your hold past a natural feel you are introducing much more of change. In the field you will default to natural and hence cant your rifle which will affect your point of impact much more since you are not zero'd to your cant.

[6.5 shooter]

Originally Posted by Dean2

NO extra margin of error is being added into the equation. If anything, error is being removed from the equation. A plumb scope on a plumb rifle will add cant error for 98% of shooters because almost everyone naturally cants a rifle when shouldered. Removing that error, and adding a scope level will always give you the most error free mounting of a rifle designed to be hunted and thus shoulder fired.

Firing a rifle like a shotgun has nothing to do with it...you have time to adjust your body to a plumb rifle where as in a shotgun it is a snap shot so cant is irrelevant.....If you take your time adjust your body to the rifle your accuracy will go up....for a snap shot in the bush either method will work.

As stated by elk (I think) if you cant your rifle buy a adjustable pad...I use to shoot with a cant because it felt good...but accuracy is not there when your into the accuracy game.

[Nyksta]

Originally Posted by 6.5 shooter

Set target at set range.. crank them turrets up or down video would be totally different.

If you can hold your rifle totally level 100% of the time at all ranges then your theory works but we NEVER hold our rifles the same every time and cant in the scope just adds one more variable.

If the scope is above the bore or offset to one side has nothing to do with sloppy shooting. if the shooter doesnt hold the scope level, then that is an error on the shooters part, and has no extra or less error due to where the bore is. Offset is not a huge issue, Canted scopes are.

[elkhunter11]

Originally Posted by Dean2

NO extra margin of error is being added into the equation. If anything, error is being removed from the equation. A plumb scope on a plumb rifle will add cant error for 98% of shooters because almost everyone naturally cants a rifle when shouldered. Removing that error, and adding a scope level will always give you the most error free mounting of a rifle designed to be hunted and thus shoulder fired.

Personally I find that if I shoulder a rifle, and it is canted, I notice that the crosshairs are canted, and I correct the hold. The crosshairs help me to hold the rife vertically, they basically act as a crude level for me.

[AndrewM]

Quoting shooting illustrated:
"In almost every riflescope manufactured, the reticle is not perfectly plumb with the adjustment turrets. Most manufactures hold that tolerance to within 5 degrees. Out to around 300 yards—the distance within which most people shoot—that error will be hardly noticeable. Leupold has an off-plumb reticle tolerance of 3 degrees for all of its scopes except the high-end Mark 6 and Mark 8s, which are allowed a maximum of 1 degree. Nightforce has a reticle-cant tolerance of .5 degree for every scope it builds; that’s right, the company mandates all its optics to be at most .5 degree off."

By leveling on your turrets you are introducing 3-5 degrees of cant. A bubble level is 1 degree of cant in accuracy.

[elkhunter11]

Originally Posted by AndrewM

Quoting shooting illustrated:
"In almost every riflescope manufactured, the reticle is not perfectly plumb with the adjustment turrets. Most manufactures hold that tolerance to within 5 degrees. Out to around 300 yards—the distance within which most people shoot—that error will be hardly noticeable. Leupold has an off-plumb reticle tolerance of 3 degrees for all of its scopes except the high-end Mark 6 and Mark 8s, which are allowed a maximum of 1 degree. Nightforce has a reticle-cant tolerance of .5 degree for every scope it builds; that’s right, the company mandates all its optics to be at most .5 degree off."

By leveling on your turrets you are introducing 3-5 degrees of cant. A bubble level is 1 degree of cant in accuracy.

That makes an excellent case for using a plumb bob to level a scope.

[AndrewM]

Originally Posted by elkhunter11

Personally I find that if I shoulder a rifle, and it is canted, I notice that the crosshairs are canted, and I correct the hold. The crosshairs help me to hold the rife vertically, they basically act as a crude level for me.

How would you know? Change the background of what you are looking at to hills and there is no way you can tell that cross hairs are canted without a bubble level.

[AndrewM]

Originally Posted by elkhunter11

That makes an excellent case for using a plumb bob to level a scope.

It does but at 3-5 degrees that is 0.4-0.7" at 1000 yards. Negligible.

[Pathfinder76]

Originally Posted by 6.5 shooter

Set target at set range.. crank them turrets up or down video would be totally different.

If you can hold your rifle totally level 100% of the time at all ranges then your theory works but we NEVER hold our rifles the same every time and cant in the scope just adds one more variable.

You are completely wrong. I’m not sure how else to say it.

[CNP]

Originally Posted by AndrewM

Have a look at my earlier post. At 1000 yards it is .07”. That’s less than 0.01” per 100 yards past 200.

BDC reticle. Canted just like your 90 degree illustration. The crosshair is zeroed at 200. Hits bullseyes at 200. Switch to the 600 yard subtension and fire. You will hit low and I don't know how far off horizontally to the left but it will be significant. You can reduce these deviations to absolute zero by making sure the rifle is level and the scope is mounted level. You're example of the path of the bullet through the bore intersecting with point of aim through the scope does not happen. Intersection only happens vertically. Your insignificant measurement now becomes significant.

[AndrewM]

Originally Posted by CNP

BDC reticle. Canted just like your 90 degree illustration. The crosshair is zeroed at 200. Hits bullseyes at 200. Switch to the 600 yard subtension and fire. You will hit low and I don't know how far off horizontally to the left but it will be significant. You can reduce these deviations to absolute zero by making sure the rifle is level and the scope is mounted level. You're example of the path of the bullet through the bore intersecting with point of aim through the scope does not happen. Intersection only happens vertically. Your insignificant measurement now becomes significant.

Yes you are using subtensions as windage. No one in there right mind would do that. You can argue until you are blue in the face. 0.7" at 1000 yards is negligible especially in a hunting situation.

[AndrewM]

Originally Posted by CNP

BDC reticle. Canted just like your 90 degree illustration. The crosshair is zeroed at 200. Hits bullseyes at 200. Switch to the 600 yard subtension and fire. You will hit low and I don't know how far off horizontally to the left but it will be significant. You can reduce these deviations to absolute zero by making sure the rifle is level and the scope is mounted level. You're example of the path of the bullet through the bore intersecting with point of aim through the scope does not happen. Intersection only happens vertically. Your insignificant measurement now becomes significant.

Spin your RZ600 straight up and down and mount it on the side of a rifle. Assume you are 2" from bore to center of crosshairs and zero at 200. At 400 yards you are only 4" off. Now you are seeing some difference but these are probably mounted on a 303 or 30-30 and you are only shooting 200 yards max and your animal is dead as you are bang on. Shoot the animal at 100 yards and you are 1" off and animal is dead.

[CNP]

Originally Posted by AndrewM

Yes you are using subtensions as windage. No one in there right mind would do that. You can argue until you are blue in the face. 0.7" at 1000 yards is negligible especially in a hunting situation.

You used the 90 degree illustration to prove something Your math was off. I just corrected your example. The only way to eliminate error is mount a scope level on a levelled rifle. I don't know why anyone would want to introduce error by intentionally not mounting a scope level on a levelled rifle. The bore must be perfectly underneath the vertical crosshair at all subtensions. It's an obvious undertaking.

[CNP]

Originally Posted by AndrewM

Spin your RZ600 straight up and down and mount it on the side of a rifle. Assume you are 2" from bore to center of crosshairs and zero at 200. At 400 yards you are only 4" off. Now you are seeing some difference but these are probably mounted on a 303 or 30-30 and you are only shooting 200 yards max and your animal is dead as you are bang on. Shoot the animal at 100 yards and you are 1" off and animal is dead.

Stop. The rz600 is meant to be installed perfectly level on a level rifle. Stop with mounting on a side mount on some Russian or Chinese POS. You don't put an rz 600 on a 303 or 30-30 either.

[elkhunter11]

Originally Posted by AndrewM

It does but at 3-5 degrees that is 0.4-0.7" at 1000 yards. Negligible.

Read my post again, I was referring to leveling a scope, not a rifle. If you think that having the crosshairs off level by 3-5 degrees, ad then dialng in the scope to shoot 1000 yards, is only going to result in an error of .4-.7" you might want to check your math.

[Pathfinder76]

Originally Posted by CNP

BDC reticle. Canted just like your 90 degree illustration. The crosshair is zeroed at 200. Hits bullseyes at 200. Switch to the 600 yard subtension and fire. You will hit low and I don't know how far off horizontally to the left but it will be significant. You can reduce these deviations to absolute zero by making sure the rifle is level and the scope is mounted level. You're example of the path of the bullet through the bore intersecting with point of aim through the scope does not happen. Intersection only happens vertically. Your insignificant measurement now becomes significant.

CNP, your scope is canted.

[Pathfinder76]

Originally Posted by elkhunter11

Read my post again, I was referring to leveling a scope, not a rifle. If you think that having the crosshairs off level by 3-5 degrees, ad then dialng in the scope to shoot 1000 yards, is only going to result in an error of .4-.7" you might want to check your math.

Deflect, deflect, deflect.

Again. Your scope needs to be level. Your rifle no.

[AndrewM]

Originally Posted by chuck

Deflect, deflect, deflect.

No doubt. The scope is level. The crosshairs are not canted, the rifle is.

[Pathfinder76]

Originally Posted by AndrewM

No doubt. The scope is level. The crosshairs are not canted, the rifle is.

Mind blowing really.

[elkhunter11]

Originally Posted by chuck

Deflect, deflect, deflect.

I specifically used the word scope, since I was referring to leveling the scope, but you are so anxious to argue, that you never bothered to read my post properly.

Originally Posted by elkhunter11 View Post
That makes an excellent case for using a plumb bob to level a scope.

Actually , I was just about to mention your link, where Mr Tubb, stated that 1 degree of cant in the scope will result in 6" at 1000 yards, So 3-5 degrees would be 18-30" at 1000 yards.

https://www.youtube.com/watch?v=Su1V...ature=youtu.be

[AndrewM]

Originally Posted by CNP

You used the 90 degree illustration to prove something Your math was off. I just corrected your example. The only way to eliminate error is mount a scope level on a levelled rifle. I don't know why anyone would want to introduce error by intentionally not mounting a scope level on a levelled rifle. The bore must be perfectly underneath the vertical crosshair at all subtensions. It's an obvious undertaking.

Where is my math off? Please correct it.
You intentionally not mount a scope on a level rifle level so you can offset your natural cant. In the field and especially in a hunting situation where your heart is pumping, you will go to a natural position which means your CROSSHAIRS are canted if you level your scope and your rifle. By canting your CROSSHAIRS you add much change than starting with a canted rifle level crosshairs and a canted rifle.
Being repeatable is way more important than trying to force yourself to do something that isn't natural.

[AndrewM]

Originally Posted by elkhunter11

I specifically used the word scope, since I was referring to leveling the scope, but you are so anxious to argue, that you never bothered to read my post properly.



Actually , I was just about to mention your link, where Mr Tubb, stated that 1 degree of cant in the scope will result in 6" at 1000 yards, So 3-5 degrees would be 18-30" at 1000 yards.

https://www.youtube.com/watch?v=Su1V...ature=youtu.be

Once again. The rifle is canted. The SCOPE is level!

[elkhunter11]

Originally Posted by AndrewM

Once again. The rifle is canted. The SCOPE is level!

You are mixing up posts and confusing yourself, I was specifically referring to the post you made where you mentioned that the turrets could be 3-5 degrees off from the crosshairs, that is why I quoted that post in my reply. I used the word scope, because I was referring to using a plumb bob to level a scope, instead of using a level on the turret.

[CNP]

Originally Posted by AndrewM

Where is my math off? Please correct it.
You intentionally not mount a scope on a level rifle level so you can offset your natural cant. In the field and especially in a hunting situation where your heart is pumping, you will go to a natural position which means your CROSSHAIRS are canted. By canting your CROSSHAIRS you add much change than starting with a canted rifle level crosshairs and a canted rifle.
Being repeatable is way more important than trying to force yourself to do something that isn't natural.

Your math was off because you calculated a horizontal intersection down range. I told you there is no intersection horizontally. That is truth. There can only be intersection vertically and we are not talking about gravity or trajectory. We are talking about horizontal tracking. If the scope is not level and it's not if it's on a canted rifle, horizontal tracking becomes greater as the target distance increases. There is no divergence somewhere down range...…..it gets more pronounced all the time. Ingenius isn't it....

[6.5 shooter]

Originally Posted by Nyksta

If the scope is above the bore or offset to one side has nothing to do with sloppy shooting. if the shooter doesnt hold the scope level, then that is an error on the shooters part, and has no extra or less error due to where the bore is. Offset is not a huge issue, Canted scopes are.

Uhhh???? so then by your measure why do rifle makers go to such pains to make sure there mounting holes or dovetails are machined plumb and square to the bore??? go buy an old cooey screw in a set of side mount rings and go shoot some groups...the bullet only imparts the target at the intersection of the line of sight and the line of the bore at ONE distance otherwise you are left or right of the target......There is a reason that sights are mounted over the bore rather then on the side of the rifle....As for the artillery reference some where else in this thread.....recoil is a BIG factor why the sight is mounted to the side of the gun also it is hard to see a target in the distance if you have to look through the barrel of your artillery piece.....

[AndrewM]

As Mr Tubb stated: 1 degree of cant in the scope will result in 6" at 1000 yards. Should work out to 3" with a 0.5 degree cant.
One degree of cant on a rifle with a level reticle you only get 0.07" at 1000 yards.
You are far more likely to cant your rifle and your reticle if you line up both straight up and down.

[Smokinyotes]

I never realized mounting a scope on a rifle was such a difficult technical process. I must have been doing it wrong all these years. I just put a level on the rifle and then use a level and plumb line to mount the scope. For hunting I don’t worry about cant. I just hold the rifle so the reticle looks level to my eye and pull the trigger. Within normal hunting ranges animals will die. I only have two dedicated long range rigs both with Near alpha mounts, NXS scopes and bubble levels so cant has never really been a problem for me as these are just shot off a bench.

[AndrewM]

Originally Posted by CNP

Your math was off because you calculated a horizontal intersection down range. I told you there is no intersection horizontally. That is truth. There can only be intersection vertically and we are not talking about gravity or trajectory. We are talking about horizontal tracking. If the scope is not level and it's not if it's on a canted rifle, horizontal tracking becomes greater as the target distance increases. There is no divergence somewhere down range...…..it gets more pronounced all the time. Ingenius isn't it....

So if you cant your crosshairs this means you cannot zero your scope with your rifle? You aren't making any sense. There will always be crossover if you zero your scope with your rifle.

[MK2750]

This has been discussed lots.

http://www.outdoorsmenforum.ca/showthread.php?t=194468