climberguy
New member
My scope is dead on at 100 yards but it is 2 inches right at 200 yards on a dead calm day. Could this be due to the mounting? Any help would be appreciated.
Scope differences at 100 and 200 yards left to right
- Thread starter climberguy
- Start date
dogleg is correct. if the scope is not level and the bore of the rifle is not under the crosshairs it will shoot off center at longer distances. unless you have a scope level checker you can swear that the scope is level on your rifle. when in fact it is not. I have solved many arguments about whether a scope is mounted correctly on a rifle with a neat little tool made by segway.
http://www.segway-industries.com/index.html
http://www.segway-industries.com/index.html
t/c223encore
New member
Wanna know one of my alignment checks?
Put the scope on the lowest setting, if variable. And with an unloaded rifle of course stand back from a large mirror and look through the scope at the reflection of yourself looking through the scope. Center the crosshairs in the scope and check to see of the verical crosshair passes through both the center of the scope and the center of the bore at the same time. This will also tell you if your holding the rilfle level or canted.
OK so I have country boy methods of doin things /ubbthreads/images/graemlins/grin.gif But it works.
t/c223encore
Put the scope on the lowest setting, if variable. And with an unloaded rifle of course stand back from a large mirror and look through the scope at the reflection of yourself looking through the scope. Center the crosshairs in the scope and check to see of the verical crosshair passes through both the center of the scope and the center of the bore at the same time. This will also tell you if your holding the rilfle level or canted.
OK so I have country boy methods of doin things /ubbthreads/images/graemlins/grin.gif But it works.
t/c223encore
climberguy
New member
Thanks for the input, I hope that is all it is, This has been driving me crazy. The gun is a savage 112bvss and is shooting 1/2 groups at 100 and about a 3/4 inch at 200, but it is always about 2 inches to the right of my point of aim at 200.
Last edited:
dan newberry
New member
I'm gonna dissent, just a bit... /ubbthreads/images/graemlins/blush.gif
In order to cant the scope enough to cause the bullet to fall 2" to the right at 200 yards, you'd have to darned near hold the rifle sideways.
The bullet will only be dropping about 1 to 1.5 inches from 100 yards to 200 yards, so you'd really have to goober up the hold to see that much difference at 200 yards.
If the scope was that much off line, I think it would be obvious even to a novice (not that you're a novice, just saying that my wife would probably be able to notice a scope that crooked). /ubbthreads/images/graemlins/laugh.gif
I don't think parallax would be a concern here either, considering that the groups are forming tightly at 200 yards, and regularly in the same position. Two hundred yards isn't really far enough to see a bad effect from parallax anyway. (No one has mentioned parallax here yet, but I wanted to get that comment on the table anyway).
You don't mention whether you're dialing up the elevation for these 200 yard groups, but I'm guessing that you are.
When you dial the elevation up, the scope's erector is deviating to the left (causing your shots to print right). This is likely because the scope is mounted in a Leupold (Redfield JR) type windage adjustable rear mount. You probably have the scope's alignment off to one side, and have had to dial in a whole bunch of windage to get it on track. When you dial in a lot of windage, that causes the erector to rub the inside of the scope tube when you dial up (or down) and it gets pushed aside, out of line.
Check this article: http://practicalrifler.6.forumer.com/viewtopic.php?t=28
That will describe how to center your scope's erector for windage. (You'll need to remove the scope to do this).
And then this article:
http://practicalrifler.6.forumer.com/viewtopic.php?t=29 That one will help you get the scope properly mounted.
And for your reading pleasure... /ubbthreads/images/graemlins/laugh.gif
http://practicalrifler.6.forumer.com/viewtopic.php?t=38 ...read this piece on "broken scopes." It'll shed additional understanding on the inner workings of the riflescope, and the consequences of an improper mount.
If you are to tell me that the shots are moving to the right at 200 yards without a scope adjustment I'm going to have to say "you've got me there." I can see no possible way that would happen with a conventionally mounted scope.
Let us know what you discover.
Dan
In order to cant the scope enough to cause the bullet to fall 2" to the right at 200 yards, you'd have to darned near hold the rifle sideways.
The bullet will only be dropping about 1 to 1.5 inches from 100 yards to 200 yards, so you'd really have to goober up the hold to see that much difference at 200 yards.
If the scope was that much off line, I think it would be obvious even to a novice (not that you're a novice, just saying that my wife would probably be able to notice a scope that crooked). /ubbthreads/images/graemlins/laugh.gif
I don't think parallax would be a concern here either, considering that the groups are forming tightly at 200 yards, and regularly in the same position. Two hundred yards isn't really far enough to see a bad effect from parallax anyway. (No one has mentioned parallax here yet, but I wanted to get that comment on the table anyway).
You don't mention whether you're dialing up the elevation for these 200 yard groups, but I'm guessing that you are.
When you dial the elevation up, the scope's erector is deviating to the left (causing your shots to print right). This is likely because the scope is mounted in a Leupold (Redfield JR) type windage adjustable rear mount. You probably have the scope's alignment off to one side, and have had to dial in a whole bunch of windage to get it on track. When you dial in a lot of windage, that causes the erector to rub the inside of the scope tube when you dial up (or down) and it gets pushed aside, out of line.
Check this article: http://practicalrifler.6.forumer.com/viewtopic.php?t=28
That will describe how to center your scope's erector for windage. (You'll need to remove the scope to do this).
And then this article:
http://practicalrifler.6.forumer.com/viewtopic.php?t=29 That one will help you get the scope properly mounted.
And for your reading pleasure... /ubbthreads/images/graemlins/laugh.gif
http://practicalrifler.6.forumer.com/viewtopic.php?t=38 ...read this piece on "broken scopes." It'll shed additional understanding on the inner workings of the riflescope, and the consequences of an improper mount.
If you are to tell me that the shots are moving to the right at 200 yards without a scope adjustment I'm going to have to say "you've got me there." I can see no possible way that would happen with a conventionally mounted scope.
Let us know what you discover.
Dan
Dan are you sayign that even if the scope was a little crooked that it would still be close at 200? My dad had his boresited at scheels. Me and him are both dead on at 100 and are shooting about 1" so were dead on at 200. soo if were dead on at 100 shouldnt it hold true for 200. Even though distance maximizes error?
dan newberry
New member
I'm not quite sure what you're asking, but if you are sighted dead on at 100 yards, the bullet will drop about 1 to 2 inches at 200 yards (depending on bullet and velocity).
But it won't shoot 2 inches off to the side at that range unless you've got a wind issue, or you've dialed up a scope which has a tube alignment issue.
Dan
But it won't shoot 2 inches off to the side at that range unless you've got a wind issue, or you've dialed up a scope which has a tube alignment issue.
Dan
wis_sharpshooter
New member
Try moving your scope 2-4 clicks assuming you have 1/4 inch clicks and see what that does if it is still on at 100 and is on at 200 then i would say don't worry about it.
Dan Newberry,
The math involved in canting/ POI errors uses that total drop from bore line plus the height of sights above the bore-line.Using a 223 with a 55 grain bullet sighted at 200 yards for example that would be 8 inches + 1 1/2 inch divergence between line of bore and line of sight at 200 yards. That is the distance that you would hit to the side if you laid the rifle on it's side. Minus the 1 1/2" of courseIf you had it perfectly level it would also impact 8 inches low. Without getting too involved in the formula, 2 inches is approximately 21% of 9.5 inches, and since the Sine of 12 is .2079; a scope mounted 12 degrees from plumb will move the POI 2 inches at 200 yards. 12 degrees ain't much!
Climberguy hasn't said that he runs clicks between 100 and 200 yards, but (Assuming 1/4 minute clicks) for 2 clicks up to move 4 clicks right you would have to have one heck of bind going in the scope. That's not impossible, but if that was the case I bet his question would be more like "How come my POI moves sideways when I crank it up?" We need more info from Climberguy.
Dogleg
The math involved in canting/ POI errors uses that total drop from bore line plus the height of sights above the bore-line.Using a 223 with a 55 grain bullet sighted at 200 yards for example that would be 8 inches + 1 1/2 inch divergence between line of bore and line of sight at 200 yards. That is the distance that you would hit to the side if you laid the rifle on it's side. Minus the 1 1/2" of courseIf you had it perfectly level it would also impact 8 inches low. Without getting too involved in the formula, 2 inches is approximately 21% of 9.5 inches, and since the Sine of 12 is .2079; a scope mounted 12 degrees from plumb will move the POI 2 inches at 200 yards. 12 degrees ain't much!
Climberguy hasn't said that he runs clicks between 100 and 200 yards, but (Assuming 1/4 minute clicks) for 2 clicks up to move 4 clicks right you would have to have one heck of bind going in the scope. That's not impossible, but if that was the case I bet his question would be more like "How come my POI moves sideways when I crank it up?" We need more info from Climberguy.
Dogleg
Gundog,
It appears that you aren't reading the links that Dan has included. He's right on the money but it's a very complicated issue.
Read the links and do a lot of thinking.
The only thing Dan left out is the possibility of the scope base holes being drilled off center on the receiver or in teh scope base.
This is more and more common on new rifles as gun makers get rid of their skilled help and hire more and more minimum wage employees.
This would cause the scope to operate at the edge of it's adjustment range and cause the same symptom you have.
You need to read and think and read and think.
This isn't a beginners issue but if you really take the time to understand it you can save some gunsmith labor which you'll have to spend if you don't figure this out.
$bob$
It appears that you aren't reading the links that Dan has included. He's right on the money but it's a very complicated issue.
Read the links and do a lot of thinking.
The only thing Dan left out is the possibility of the scope base holes being drilled off center on the receiver or in teh scope base.
This is more and more common on new rifles as gun makers get rid of their skilled help and hire more and more minimum wage employees.
This would cause the scope to operate at the edge of it's adjustment range and cause the same symptom you have.
You need to read and think and read and think.
This isn't a beginners issue but if you really take the time to understand it you can save some gunsmith labor which you'll have to spend if you don't figure this out.
$bob$
Jack Roberts
Moderator - Deceased
Even 12 degrees is a whole lot of cant. Even my cat would find 12 degrees really weird.
Jack
Jack
Quote:
Even 12 degrees is a whole lot of cant. Even my cat would find 12 degrees really weird.
Jack
Exactly, the effect of what some think of as small scope mounting errors is huge, not small, and the longer distances magnify it. Most big-game cartridges are even worse. My point is that there are a lot of scopes off at least that far, we have all seen them.
Question; do you ah, communicate with your cat regularly? Not that there's anything wrong with that! /ubbthreads/images/graemlins/grinning-smiley-006.gif /ubbthreads/images/graemlins/laugh.gif
Dogleg
Even 12 degrees is a whole lot of cant. Even my cat would find 12 degrees really weird.
Jack
Exactly, the effect of what some think of as small scope mounting errors is huge, not small, and the longer distances magnify it. Most big-game cartridges are even worse. My point is that there are a lot of scopes off at least that far, we have all seen them.
Question; do you ah, communicate with your cat regularly? Not that there's anything wrong with that! /ubbthreads/images/graemlins/grinning-smiley-006.gif /ubbthreads/images/graemlins/laugh.gif
Dogleg
Jack Roberts
Moderator - Deceased
I don't communicate with the cat but she sure communicates with me. Absolutely anything she wants, she demands from me. She has the wife and I well trained.
Jack
Jack
climberguy
New member
No, I am not messing with my windage or elevation settings. I am sighted in dead on at 200 and about 1 inch high at 100. At 100 I am dead center, and at 200 the bullet is hitting about 1 1/2-2 inches right. Thanks
dan newberry
New member
In that case you'd have to go back and forth from 100 to 200 yards a time or two to really know what's going on here.
While it is true that a 12 degree cant could move the shot an inch or a little more at 200 yards, I think a 12 degree cant should be obvious to the shooter.
This cant that we're discussing has nothing, however, to do with how the scope is mounted. You can mount a scope on a rifle crooked (canted) and so long as you hold the vertical crosshair perpendicular with gravity (level up and down) then the shots will all fall along that vertical crosshair--even though the rifle may be canted underneath the scope. Some of the side mounted scopes for top ejecting rifles are actually an inch or more off to the left side. The rule remains basically the same for the side mounts: hold the scope, not necessarily the rifle level and your shots will fall along the vertical crosshair.
Some highpower shooters deliberately mount the scope with a bit of cant to it so that the scope is level when they hold the rifle up to their shoulder. It is natural for most of us to hold a rifle a bit canted. That's not a big deal. Canting the rifle is pretty much immaterial, canting the scope is a big no-no.
So, since you have not adjusted the windage, either one of two things has happened here:
You've either canted the scope six degrees left at 100 yards, and six right at 200 to make up twelve degrees of total cant (which, as Dogleg says, would account for the error you're seeing).
or...
Your scope has changed zero between the shooting sessions.
The reason I mention the six and six degree left/right cant is that I don't see how anyone with enough balance to stand up and walk wouldn't notice 12 degrees of cant in the scope when they were looking through it. Maybe I'm being unfair there, but 12 degrees would be a completely obvious amount of cant. /ubbthreads/images/graemlins/wink.gif
Dan
While it is true that a 12 degree cant could move the shot an inch or a little more at 200 yards, I think a 12 degree cant should be obvious to the shooter.
This cant that we're discussing has nothing, however, to do with how the scope is mounted. You can mount a scope on a rifle crooked (canted) and so long as you hold the vertical crosshair perpendicular with gravity (level up and down) then the shots will all fall along that vertical crosshair--even though the rifle may be canted underneath the scope. Some of the side mounted scopes for top ejecting rifles are actually an inch or more off to the left side. The rule remains basically the same for the side mounts: hold the scope, not necessarily the rifle level and your shots will fall along the vertical crosshair.
Some highpower shooters deliberately mount the scope with a bit of cant to it so that the scope is level when they hold the rifle up to their shoulder. It is natural for most of us to hold a rifle a bit canted. That's not a big deal. Canting the rifle is pretty much immaterial, canting the scope is a big no-no.
So, since you have not adjusted the windage, either one of two things has happened here:
You've either canted the scope six degrees left at 100 yards, and six right at 200 to make up twelve degrees of total cant (which, as Dogleg says, would account for the error you're seeing).
or...
Your scope has changed zero between the shooting sessions.
The reason I mention the six and six degree left/right cant is that I don't see how anyone with enough balance to stand up and walk wouldn't notice 12 degrees of cant in the scope when they were looking through it. Maybe I'm being unfair there, but 12 degrees would be a completely obvious amount of cant. /ubbthreads/images/graemlins/wink.gif
Dan
Dan Newberry,
It isn't getting Climberguys issue worked out, but I'll debate your points, just to have a little fun. /ubbthreads/images/graemlins/grinning-smiley-006.gif You are having fun right?
1) Quote "I think a 12 degree cant should be obvious to the shooter."
Answer:The shooter sees a straight crosshair, the rifle is mounted crooked by the shooter. Many people need someone else to tell them that their form is flawed.
2)Quote "You can mount a scope on a rifle crooked (canted) and so long as you hold the vertical crosshair perpendicular with gravity (level up and down) then the shots will all fall along that vertical crosshair--even though the rifle may be canted underneath the scope."
Answer: Now that is just plain wrong!The bullet will drop from the line of bore, which is not under the line of sight anymore. The bullet will deviate from the sight path by a percentage of what the rifle would do lieing flat on it's side. The percentage is calculated by using the Sine of the cant angle as a percentage. They teach that in Grade six now, but I still make a pretty good living explaining it in the oil drilling industry!
3)Quote "Some highpower shooters deliberately mount the scope with a bit of cant to it so that the scope is level when they hold the rifle up to their shoulder."
Answer: Yes, and they also have to make windage corrections at each range change. The deliberate cant helps some lock in their form, for many it is worthwhile.
4) Quote:"That's not a big deal. Canting the rifle is pretty much immaterial, canting the scope is a big no-no."
Answer: You have got that exactly backwards. The canted rifle is the whole problem! A canted scope with a Plex or crosshair LEADS to the rifle being mounted canted, which is the problem. Think about it, if you had a dot reticle you wouldn't see the error, but if the rifle is canted all shots will still fall to that side.
5)Quote:"Your scope has changed zero between the shooting sessions."
Is that all ya got? /ubbthreads/images/graemlins/smile.gif Hey Climberguy, is your 100 yard windage still dead on? Thought so!
Having fun yet? /ubbthreads/images/graemlins/grinning-smiley-006.gif
Dogleg
It isn't getting Climberguys issue worked out, but I'll debate your points, just to have a little fun. /ubbthreads/images/graemlins/grinning-smiley-006.gif You are having fun right?
1) Quote "I think a 12 degree cant should be obvious to the shooter."
Answer:The shooter sees a straight crosshair, the rifle is mounted crooked by the shooter. Many people need someone else to tell them that their form is flawed.
2)Quote "You can mount a scope on a rifle crooked (canted) and so long as you hold the vertical crosshair perpendicular with gravity (level up and down) then the shots will all fall along that vertical crosshair--even though the rifle may be canted underneath the scope."
Answer: Now that is just plain wrong!The bullet will drop from the line of bore, which is not under the line of sight anymore. The bullet will deviate from the sight path by a percentage of what the rifle would do lieing flat on it's side. The percentage is calculated by using the Sine of the cant angle as a percentage. They teach that in Grade six now, but I still make a pretty good living explaining it in the oil drilling industry!
3)Quote "Some highpower shooters deliberately mount the scope with a bit of cant to it so that the scope is level when they hold the rifle up to their shoulder."
Answer: Yes, and they also have to make windage corrections at each range change. The deliberate cant helps some lock in their form, for many it is worthwhile.
4) Quote:"That's not a big deal. Canting the rifle is pretty much immaterial, canting the scope is a big no-no."
Answer: You have got that exactly backwards. The canted rifle is the whole problem! A canted scope with a Plex or crosshair LEADS to the rifle being mounted canted, which is the problem. Think about it, if you had a dot reticle you wouldn't see the error, but if the rifle is canted all shots will still fall to that side.
5)Quote:"Your scope has changed zero between the shooting sessions."
Is that all ya got? /ubbthreads/images/graemlins/smile.gif Hey Climberguy, is your 100 yard windage still dead on? Thought so!
Having fun yet? /ubbthreads/images/graemlins/grinning-smiley-006.gif
Dogleg
dan newberry
New member
Dogleg,
Let's take on these issues one by one, so that way our audience doesn't get lost in the rhetoric. /ubbthreads/images/graemlins/laugh.gif
I said, then you said:
2)Quote "You can mount a scope on a rifle crooked (canted) and so long as you hold the vertical crosshair perpendicular with gravity (level up and down) then the shots will all fall along that vertical crosshair--even though the rifle may be canted underneath the scope."
Answer: Now that is just plain wrong!The bullet will drop from the line of bore, which is not under the line of sight anymore. The bullet will deviate from the sight path by a percentage of what the rifle would do lieing flat on it's side. The percentage is calculated by using the Sine of the cant angle as a percentage. They teach that in Grade six now, but I still make a pretty good living explaining it in the oil drilling industry!
Look at this crude drawing I cooked up just for this post:
This picture represents a canted rifle underneath a level scope. You're looking at the buttstock of the rifle, and on through the scope. The orange circle is the approximate location of the bore of the rifle. The blue dots represent the fall of the shots as they go downrange; they fall with gravity along a line which is represented by the vertical crosshair in the scope.
What we must concern ourselves with to understand this issue is the scope and the bullet path. When you dial the scope's erector to zero for windage, you are essentially aligning it with the bullet path--not the barrel!
So if a scope is mounted slightly canted, but held level, the bore of the canted rifle would only be off to the side a fraction of an inch (perhaps 1/16 to 1/8 inch) underneath. It would look something like this:
Is it important that the bore isn't 100 percent underneath the scope's vertical crosshair? Actually, no.
Think about it this way:
If you have the scope dialed to a perfect 100 yard zero with one particular load, and then you switch to another load, you'll likely note that your windage zero will change. Has the scope moved? No. Has the barrel changed? No. Only the direction that the barrel is throwing the shots has changed. Barrels, by their very nature, throw shots here, there, and yonder. /ubbthreads/images/graemlins/laugh.gif So you must dial the scope's erector to follow the general path of the new load to get your zero. This may take the scope's centerline well away from the boreline--but that's not what's important. Bullet path and boreline are two different things.
You see, the scope's erector is never actually aligned with the bore of the rifle to begin with--it is aligned with the path of whatever bullets you are setting the zero for.
So I steadfastly maintain that you can have a canted rifle underneath a level scope and keep your windage zero for all ranges.
I'll be offline until late tonight. Gotta go help the Lion's Club run our little carnival we put on each year. I enjoy friendly discussion, and I'll get back as soon as I can...
Respectfully,
Dan
Let's take on these issues one by one, so that way our audience doesn't get lost in the rhetoric. /ubbthreads/images/graemlins/laugh.gif
I said, then you said:
2)Quote "You can mount a scope on a rifle crooked (canted) and so long as you hold the vertical crosshair perpendicular with gravity (level up and down) then the shots will all fall along that vertical crosshair--even though the rifle may be canted underneath the scope."
Answer: Now that is just plain wrong!The bullet will drop from the line of bore, which is not under the line of sight anymore. The bullet will deviate from the sight path by a percentage of what the rifle would do lieing flat on it's side. The percentage is calculated by using the Sine of the cant angle as a percentage. They teach that in Grade six now, but I still make a pretty good living explaining it in the oil drilling industry!
Look at this crude drawing I cooked up just for this post:
This picture represents a canted rifle underneath a level scope. You're looking at the buttstock of the rifle, and on through the scope. The orange circle is the approximate location of the bore of the rifle. The blue dots represent the fall of the shots as they go downrange; they fall with gravity along a line which is represented by the vertical crosshair in the scope.
What we must concern ourselves with to understand this issue is the scope and the bullet path. When you dial the scope's erector to zero for windage, you are essentially aligning it with the bullet path--not the barrel!
So if a scope is mounted slightly canted, but held level, the bore of the canted rifle would only be off to the side a fraction of an inch (perhaps 1/16 to 1/8 inch) underneath. It would look something like this:
Is it important that the bore isn't 100 percent underneath the scope's vertical crosshair? Actually, no.
Think about it this way:
If you have the scope dialed to a perfect 100 yard zero with one particular load, and then you switch to another load, you'll likely note that your windage zero will change. Has the scope moved? No. Has the barrel changed? No. Only the direction that the barrel is throwing the shots has changed. Barrels, by their very nature, throw shots here, there, and yonder. /ubbthreads/images/graemlins/laugh.gif So you must dial the scope's erector to follow the general path of the new load to get your zero. This may take the scope's centerline well away from the boreline--but that's not what's important. Bullet path and boreline are two different things.
You see, the scope's erector is never actually aligned with the bore of the rifle to begin with--it is aligned with the path of whatever bullets you are setting the zero for.
So I steadfastly maintain that you can have a canted rifle underneath a level scope and keep your windage zero for all ranges.
I'll be offline until late tonight. Gotta go help the Lion's Club run our little carnival we put on each year. I enjoy friendly discussion, and I'll get back as soon as I can...
Respectfully,
Dan