Question on leveling a scope "crosshairs"

[c4snipar]

Thanks for all that commented. It looks like majority of the people here agree to level it, but as I mentioned if I choose to go this route it will bother the hell out of me seeing crooked crosshair by the way I hold. I guess I have to give up something.....hmmm

For the person who asked, it's 100 yard for now and maybe go up to 300 in the future?

 

[Doco Overboard]

I try to line up the vertical reticle to the center line of the bore as close as possible to prevent the windage and elevation adjustments from affecting each other over a great distance. My thinking is that the bullet doesn't think but reacts to gravity and wind deflection regardless of the position of the rifle whether its vertically plumb or exactly 90 degrees right or left, exterior ballistics comes into play then. A canted rifle is not going to make the trajectory change gravity is straight up and down but may make it hard to keep good dope. Eye position on the convex lens would be of more concern to me which will make cross-hairs look crooked.

 

[Qbeam]

Wow, Tubbs doesn't know what he is doing then.

Hard to say: http://www.accurateshooter.com/optics/canting-effect-on-point-of-impact/


Effects of Rifle Canting at Long Range — David Tubb Explains

Eleven-Time NRA National High Power Champion David Tubb knows a bit about long-range shooting. One of the key factors in long-range accuracy is making sure that the tilt/cant of your rifle does not change throughout your shot string. In the clip below, the first in McMillan’s Master Class Video series, David Tubb explains the importance of keeping your rifle level. He explains that, at 1000 yards, your Point of Impact can change dramatically by canting the rifle either right or left. David states that, when shooting at 1000 yards, if your rifle is level and your shot is centered-up on a 72″ (six-foot) square target, you can actually put your next shot OFF PAPER by canting your rifle. That means you can move Point of Impact (POI) three feet or more, just by canting your rifle!

Bryan Litz confirms Tubb’s observation. Bryan tells us that, as a general rule of thumb (for common cartridges), a 1° cant will produce five (5) inches of lateral displacement at 1000 yards. Thus, if you cant your rifle just 8°, the POI would move 40″ from the center of the target, putting the shot off the edge of a 72″-wide target.

David explains that, after one of his students has made two or three 1000-yard, X-Ring hits with a LEVEL rifle, “then I’ll have him take his rifle, and cant it to the right. I’ll have him shoot a shot. He will MISS the six-foot-square frame off to the right. Then I’ll have him cant his gun to the left and shoot another shot. He will miss the six-foot-square frame to the left.”

Sounds like if you cant the rifle, you need to be consistent.

Q

 

[Doco Overboard]

I also bet none of them is shooting a rifle with crooked cross hairs either, hard to argue with the master. I wonder how all that that pans out with elevation changes?

 

[Qbeam]

I also bet none of them is shooting a rifle with crooked cross hairs either, hard to argue with the master. I wonder how all that that pans out with elevation changes?

I would think that if the cant is consistent (critical part), it should be ok for that shooter just that there is an offset. The article talks about bore to scope offset and the issues with larger objective scopes.

Q

 

[Mdeng]

Thanks for all that commented. It looks like majority of the people here agree to level it, but as I mentioned if I choose to go this route it will bother the hell out of me seeing crooked crosshair by the way I hold. I guess I have to give up something.....hmmm

For the person who asked, it's 100 yard for now and maybe go up to 300 in the future?

If the distance is only 100/300 yards it won't really matter.

 

[Pinecone]

Pine,

If you see my next post, it clarifies that you can cant if you wish, but the scope should be level with the rifle. Leveling the scope with the cant, induces the added horizontal and vertical components if the same cant angle is not maintained.

Q

I answered your first post as I read it.

And I agree with you, level the scope to the world. And the minor amount of offset will do little.

FYI, look a the M1 sniper rifles. And any Win 94 with a scope mounted.

 

[Pinecone]

I try to line up the vertical reticle to the center line of the bore as close as possible to prevent the windage and elevation adjustments from affecting each other over a great distance. My thinking is that the bullet doesn't think but reacts to gravity and wind deflection regardless of the position of the rifle whether its vertically plumb or exactly 90 degrees right or left, exterior ballistics comes into play then. A canted rifle is not going to make the trajectory change gravity is straight up and down but may make it hard to keep good dope. Eye position on the convex lens would be of more concern to me which will make cross-hairs look crooked.

Think of this. If you held your rifle 90 degrees canted. If you leveled your scope to the rifle, elevation would be windage and windage would be elevation.

Centerline of bore means nothing.

If you held your rifle 90 degrees canted, but leveled the scope to the world, elevation would be pure elevation and windage would be pure windage. And all would be right with the world.

The ONLY downside of having the scope offset from the bore, is dealing with the issue of windage at varying ranges, which I addressed in an earlier post.

 

[Pinecone]

I would think that if the cant is consistent (critical part), it should be ok for that shooter just that there is an offset. The article talks about bore to scope offset and the issues with larger objective scopes.

Q

Yes, the cant must be consistent. For long range shooting, put a scope level on, but have it indexed to the cross hairs.

And if you have your rifle set up for no cant, and you cant it, remember, the bore is aimed well above the line of sight. And when you cant it, a portion of that UP becomes sideways.

 

[c4snipar]

Finally gotten it straighten out with a bid pod.

1. Level counter top
2. Level rifle flat top piccatinny rail
3. Level scope
4. Hang a target with a string
5. Aim through the scope and the crosshair was straight.

I don't know what I have done wrong or the stranger thing with the gun wise.

Again, thanks all of you!

 

[outrider58]

For a bench gun, I don't see what all the hooplah was.

 

[Major03]

Not adding to the debate of level to your cant or level to the rifle. I level to the rifle.

If that's your bag, a quick way to level a scope to the rifle is to use a feeler gauge or a deck of cards.

This is assuming you have a rail site base and a tactical scope that has a flat portion under the elevation and windage turrets.

Put the gauge in between the base and the flat portion of the scope.

Tighten the screws on your rings just enough to keep the scope from moving while you remove the gauge. Tighten to spec after it is removed.

Granted it's a down and dirty, but I've verified with a plumb bob on three rifles I've done this method with and haven't had to adjust yet.

YMMV.

 

[Doco Overboard]

Think of this. If you held your rifle 90 degrees canted. If you leveled your scope to the rifle, elevation would be windage and windage would be elevation.

Centerline of bore means nothing.

If you held your rifle 90 degrees canted, but leveled the scope to the world, elevation would be pure elevation and windage would be pure windage. And all would be right with the world.

The ONLY downside of having the scope offset from the bore, is dealing with the issue of windage at varying ranges, which I addressed in an earlier post.

In my world, windage would be elevation and windage would be the elevation knob when my rifle was turned 90 degrees unless I went all the way to 180 then it would be back to right again. And then would it shoot low? Unless I mounted the scope purposefully to use the windage for the elevation adjustment from the get go for a reason and even then the vertical cross-wire would cut the center of the action and the center line of the bore. The OP has mounted his scope on top of the receiver not the side. Ideally, mechanical center line through the body of an installed scope should be parallel with the center line through the receiver and bore. P143 The Mauser Bolt Actions, section II Jerry Kunhausen.

 

[Pinecone]

In my world, windage would be elevation and windage would be the elevation knob when my rifle was turned 90 degrees unless I went all the way to 180 then it would be back to right again. And then would it shoot low? Unless I mounted the scope purposefully to use the windage for the elevation adjustment from the get go for a reason and even then the vertical cross-wire would cut the center of the action and the center line of the bore. The OP has mounted his scope on top of the receiver not the side. Ideally, mechanical center line through the body of an installed scope should be parallel with the center line through the receiver and bore. P143 The Mauser Bolt Actions, section II Jerry Kunhausen.

If you are talking about them both being vertical I agree.

Notice it does NOT say that the mechanical center line of the scope must pass through the bore.

Where people seem to get caught up is the difference between having the scope canted from vertical when shooting, versus having the rifle canted (but with the scope vertical).

These are two different cases.

No matter what, the scope cross hairs must be aligned with the world when you shoot.

If you naturally hold your rifle vertically, great, you can reference the scope to the rifle. But, many people naturally hold their rifle with a cant (see Tubbs). In that case, you need to mount the scope, so that when you hold your rifle naturally, your scope is aligned (vertical/horizontal) to the world, NOT the rifle.

 

[dist1646]

Tubb does not say that canting the scope makes any significant difference, he states that canting the rifle makes the difference in point of impact. That is true, canting the rifle differently between shots makes a difference in point of impact. If you have watched the way Tubb sets up his rifles, you will note that he levels his sights to the way he naturally cants the rifle while in position. Setting up the sight to be level with the way you naturally hold the rifle will produce the most consistency! The vast majority of people will naturally repeat their rifles cant to a much higher degree of consistency than they will when they try to force the rifle to be level. My advise is to hold the rifle in your natural position and have someone level the scope accordingly, so that it fits and works for you.

 

[outrider58]

. My advise is to hold the rifle in your natural position and have someone level the scope accordingly, so that it fits and works for you.

Any true vertical line(edge of a building is perfect for this) makes this easy.

 

[Pinecone]

Tubb does not say that canting the scope makes any significant difference, he states that canting the rifle makes the difference in point of impact. That is true, canting the rifle differently between shots makes a difference in point of impact. If you have watched the way Tubb sets up his rifles, you will note that he levels his sights to the way he naturally cants the rifle while in position. Setting up the sight to be level with the way you naturally hold the rifle will produce the most consistency! The vast majority of people will naturally repeat their rifles cant to a much higher degree of consistency than they will when they try to force the rifle to be level. My advise is to hold the rifle in your natural position and have someone level the scope accordingly, so that it fits and works for you.

Actually, it is canting the SIGHTS that screws things up.

But basically, this is what I have been saying. Level your scope to the world, when you hold your rifle the way YOU hold it.

 

[dist1646]

Actually, it is canting the SIGHTS that screws things up.

But basically, this is what I have been saying. Level your scope to the world, when you hold your rifle the way YOU hold it.

I think you just contradicted yourself.

 

[lazarus]

Have the scope level. If the cross hairs look canted they look canted. If you ever do come-ups or anything like that, mildot, etc you need the scope itself level or else you'll be off. The longer the distance the more you'd be off. At a hundred yard unless you are going hamster with your rifle you'll probably be an inch off at most, but if you have a scope with a hold over and are shooting at something at 300yds with the scope zeroed at 100yds you might be off 2-4 inches with a typical holding cant.

I level my scopes, but I also tend to hold my rifles about a degree or two tilted and it looks a little odd, but if I do hold over, etc it is important to know you are raising it properly.

 

[lazarus]

Any true vertical line(edge of a building is perfect for this) makes this easy.

It is how I level all my scopes. I've got a nice fence post about 40yds away I use to level all my scopes. Of course I also hope my neighbors don't see me aiming a rifle out my window...but I setup on my counter at the backside of my house aiming out the front and then level the scope.

Oh and I am odd, but I took a plumb line to my neighbor's fence post and it is plumb.