Scope Levels- Why?

[An Idahoan]

To Me It is very simple, If you make everything true and level. you wont have to compensate for it.
Start right and end right. I know and have shot against some shooters that cant their rifles. I also often wondered how good they would be if they didn't cant the rifle. [...]

What the math and geometry are saying is that the compensation you speak of can be all of 0.3" at all ranges (from muzzle to infinity) which is approximately one bullet diameter. This is hardly a problem when one considers the advantages that I stated above. I have yet to have someone demonstrate that my math/geometry is wrong. If I am wrong, I badly want someone to show me how.

 

[J E Custom]

What the math and geometry are saying is that the compensation you speak of can be all of 0.3" at all ranges (from muzzle to infinity) which is approximately one bullet diameter. This is hardly a problem when one considers the advantages that I stated above. I have yet to have someone demonstrate that my math/geometry is wrong. If I am wrong, I badly want someone to show me how.

The error has to increase with distance, so just like spin drift, it is .01 MOA at 100 yards with my load. at 1000 yards it becomes 1.0 MOA . Any alignment error gets greater, the farther distance it travels.

If you draw a straight line and make it 1o off, it will stay 1o off for ever but the distance from the targeted point with no 1o offset will get greater the farther the distance gets.

To a smith like myself and many more, any error is a problem so we avoid any thing that is not true and level. Nothing is perfect, but we try to get as close to it as possible so top performance is possible.

No one is really wrong to the point that they cant compensate for errors, But it is just easier to make something easier so you can concentrate on other variable things than need to be compensated for like wind. If everything is true and level, wind value is normally one adjustment. If canting the rifle, you have to add the wind effect and the canting effect that can be both more wind and elevation in addition to wind value.

J E CUSTOM

 

[An Idahoan]

The error has to increase with distance, so just like spin drift, it is .01 MOA at 100 yards with my load. at 1000 yards it becomes 1.0 MOA . Any alignment error gets greater, the farther distance it travels. [...]

J E Custom,

I get what you're saying. It is a problem with an easy solution. Instead of making the bore axis and optical axis converge at your zero (scenario 3b), make the bore axis parallel to the optical axis (scenario 3a). If you have a 10 degree left cant, then at 100 yards (or 200 yards), adjust for a bullet impact of 0.30" left of hold. The result will be that the lateral (or horizontal) separation between the bore and optical axes at the rifle is a constant 0.30" from 0 through infinity. If 0.30" at all ranges is unworkable, then I suppose you'd better make sure that your scope reticle and bore are on the same plumb. Just as long as people are making an informed decision and are not led to believe that scenarios 3a and 3b as outlined above have the same disastrous results are will occur in scenario 2 outlined above.

Paul

 

[Canadian Bushman]

J E Custom,

I get what you're saying. It is a problem with an easy solution. Instead of making the bore axis and optical axis converge at your zero (scenario 3b), make the bore axis parallel to the optical axis (scenario 3a). If you have a 10 degree left cant, then at 100 yards (or 200 yards), adjust for a bullet impact of 0.30" left of hold. The result will be that the lateral (or horizontal) separation between the bore and optical axes at the rifle is a constant 0.30" from 0 through infinity. If 0.30" at all ranges is unworkable, then I suppose you'd better make sure that your scope reticle and bore are on the same plumb. Just as long as people are making an informed decision and are not led to believe that scenarios 3a and 3b as outlined above have the same disastrous results are will occur in scenario 2 outlined above.

Paul

In order for that to work the rifle must still be held true every time its fired.
Just because your scope isnt straight doesnt alleviate variable canting errors in the field.

Also, if you just mount your scope true, you dont have to calculate how far off your bullet should impact, nor would you have to measure your scope cant.

 

[An Idahoan]

In order for that to work the rifle must still be held true every time its fired.
Just because your scope isnt straight doesnt alleviate variable canting errors in the field.

[...]
My hope is that this will help people see that if horizontal zero issues are understood and properly accounted for when zeroing the rifle, someone can shoot a rifle with the optical axis and bore "canted" as long as the reticle consistently plumb (and therefore the need for a level).
[...]

Agreed Canadian Bushman! This is what I have been saying the whole time. Yes, levels are a must for long range.

 

[Canadian Bushman]

Three way adjustable butt plates are quite affordable and also allow you to custom fit your rifle as well as keep your optic plumb and true. Just in case anyone was debating whether or not to purposely cant their rifle.

 

[Litrfoot]

For those that are having a hard time understanding this, this will prove it to you. Set up a target at 500 yds with a big cross of tape "+", make sure its level! Now put your rifle in a sled and introduce a small cant error on the cross of the target. Now strap the rifle down so it can't move. Now looking through the scope adjust the wind and elevation and watch what happens to the reticle. This is like a tall target test at 100 yards, however it really give you a better idea how extreme the errors can be at longer yardages.

 

[LaHunter]

J E Custom,

I get what you're saying. It is a problem with an easy solution. Instead of making the bore axis and optical axis converge at your zero (scenario 3b), make the bore axis parallel to the optical axis (scenario 3a). If you have a 10 degree left cant, then at 100 yards (or 200 yards), adjust for a bullet impact of 0.30" left of hold. The result will be that the lateral (or horizontal) separation between the bore and optical axes at the rifle is a constant 0.30" from 0 through infinity. If 0.30" at all ranges is unworkable, then I suppose you'd better make sure that your scope reticle and bore are on the same plumb. Just as long as people are making an informed decision and are not led to believe that scenarios 3a and 3b as outlined above have the same disastrous results are will occur in scenario 2 outlined above.

Paul

I am no mathematician or ballistic expert, but the bore axis is never parallel to the optical axis. If they were, then the bullet would never impact at the POA. The line of sight is straight, but the bore is always canted in the upward direction. If the bore is off to the left or right due to not being in the same vertical axis (when the reticle is true but the rifle is canted), then the barrel has to be canted upward and either to the left or right slightly. Would this not cause the bullet to start its journey with some left or right 'english' (depending on the rifle cante)?

 

[yobuck]

I'm currently reading Ryan Cleckner's "Long Range Shooting Handbook" and he explained the reason he doesn't use scope levels is because he's never seen one accurate enough to make a critical difference. When every degree matters at long range that bubble level just isn't going to give you 100% accuracy. If your eye doesn't naturally pick up plumb / level easily than perhaps they could help to some degree, I lived a former life as a frame carpenter so my eye naturally sees anything out of level ... drives me nuts! lol

I'm also not saying my eye is better than a bubble level, but like Ryan I feel they are at least comparable. Now if we get into digital levels that are gaining traction in the trades then we may have something to talk about given the higher levels (pun intended) of accuracy they can provide.

I think your background helps more than you realize.
How many times have you looked at something and thought it might not be plumb or level, that when you actually checked you found your instincs were wrong? id say very few times if any.
As for the scope levels, id let the results be telling you if you need one.

 

[An Idahoan]

I am no mathematician or ballistic expert, but the bore axis is never parallel to the optical axis. If they were, then the bullet would never impact at the POA. The line of sight is straight, but the bore is always canted in the upward direction. If the bore is off to the left or right due to not being in the same vertical axis (when the reticle is true but the rifle is canted), then the barrel has to be canted upward and either to the left or right slightly. Would this not cause the bullet to start its journey with some left or right 'english' (depending on the rifle cante)?

I should have clarified that the two axes are parallel only when viewed from above. When viewed from the side, it is a different story. See my post above with diagrams.

 

[JAYgs8163]

I use them because every little edge matters and they work.

 

[J E Custom]

I am no mathematician or ballistic expert, but the bore axis is never parallel to the optical axis. If they were, then the bullet would never impact at the POA. The line of sight is straight, but the bore is always canted in the upward direction. If the bore is off to the left or right due to not being in the same vertical axis (when the reticle is true but the rifle is canted), then the barrel has to be canted upward and either to the left or right slightly. Would this not cause the bullet to start its journey with some left or right 'english' (depending on the rifle cante)?

I didn't say it was horizontally parallel but that the bore line and the site line should be vertically parallel (one on top of the other). With convergence, at some point the bore centerline will be above the optical centerline (Line of site).

J E CUSTOM

 

[LaHunter]

I didn't say it was horizontally parallel but that the bore line and the site line should be vertically parallel (one on top of the other). With convergence, at some point the bore centerline will be above the optical centerline (Line of site).

J E CUSTOM

I thought I was quoting Idahoan. J.E. I think I agree with you, if the bore and the scope are not in the same vertical plane, you introduce potential issues with accuracy / precision.

 

[J E Custom]

I thought I was quoting Idahoan. J.E. I think I agree with you, if the bore and the scope are not in the same vertical plane, you introduce potential issues with accuracy / precision.

Sorry !!!!! to much time on my hands with this quarantine. Back to work.

J E CUSTOM