Broz
Well-Known Member
Interesting Bill, Thanks!
Jef
Jef
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Bigcat_hunter
Well-Known Member
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Use this guide;Reticle Perpendicularity
J E Custom
Well-Known Member
The reason for leveling the action first and then leveling the scope reticle is because the barrel center line and the scope center line are not parallel, they form a triangle and converge at some
point. If the reticle is not level with the action, as elevation is added horizontal POI will shift
left or right depending on the error in level and distance.
I know match shooters that cant there rifles naturally and when they increase distance they add Windage to compensate for the change.
If everything is level there will be almost no Windage change when going from one distance to another other than that caused by the wind.
One way to test the reticle is to set up at 200 yards and after zeroing start cranking in elevation
(4 MOA between shots) aiming at the same point the vertical string will start to move off the vertical line if the scope and scope are not level with each other.
So in my opinion, leveling the action and the scope reticle to each other will minimize the error when elevation changes are necessary.
J E CUSTOM
point. If the reticle is not level with the action, as elevation is added horizontal POI will shift
left or right depending on the error in level and distance.
I know match shooters that cant there rifles naturally and when they increase distance they add Windage to compensate for the change.
If everything is level there will be almost no Windage change when going from one distance to another other than that caused by the wind.
One way to test the reticle is to set up at 200 yards and after zeroing start cranking in elevation
(4 MOA between shots) aiming at the same point the vertical string will start to move off the vertical line if the scope and scope are not level with each other.
So in my opinion, leveling the action and the scope reticle to each other will minimize the error when elevation changes are necessary.
J E CUSTOM
Broz
Well-Known Member
So in my opinion, leveling the action and the scope reticle to each other will minimize the error when elevation changes are necessary.
J E CUSTOM
Thanks JE and I agree. Also your test is something I have referred to earlier as the final thing being "shoot it in" Because we all know not all reticles are mounted in the scope true to the travel of the turret either. If so, or in a "perfect world" we would be done after we trued the reticle to a plumb line. But that just gets us close. Many will be fine, but some need final adjusting.
Jeff
The reason for leveling the action first and then leveling the scope reticle is because the barrel center line and the scope center line are not parallel, they form a triangle and converge at some
point. If the reticle is not level with the action, as elevation is added horizontal POI will shift
left or right depending on the error in level and distance.
I know match shooters that cant there rifles naturally and when they increase distance they add Windage to compensate for the change.
If everything is level there will be almost no Windage change when going from one distance to another other than that caused by the wind.
One way to test the reticle is to set up at 200 yards and after zeroing start cranking in elevation
(4 MOA between shots) aiming at the same point the vertical string will start to move off the vertical line if the scope and scope are not level with each other.
So in my opinion, leveling the action and the scope reticle to each other will minimize the error when elevation changes are necessary.
J E CUSTOM
When I posed this same question to Norm Houle. his point was that mathematically you are correct. However, under real shooting conditions, it's not a factor because of all of the other things that affect the bullet. Personally, I am much steadier with a canted stock and I feel that this makes up for the slight horizontal error introduced by canting my stock. It's not for everyone but it's worth a try.
J E Custom
Well-Known Member
When I posed this same question to Norm Houle. his point was that mathematically you are correct. However, under real shooting conditions, it's not a factor because of all of the other things that affect the bullet. Personally, I am much steadier with a canted stock and I feel that this makes up for the slight horizontal error introduced by canting my stock. It's not for everyone but it's worth a try.
When I shot NRA High power we shot 200, 300, 600 and 1000 yards and it was very important
to me to have a level on the rifle (These were iron site matches)so I didn't cant the rifle and elevation changes were very simple.
I knew lots of shooters that "Did" cant there rifles and used Windage to correct for this as they elevated.
others that liked the feel of a canted stock/rifle went to an adjustable but stock and canted the butt stock
to get this feel/fit to there shoulder. You will see adjustable butt stocks on many 3 position+ match rifles
for this reason (Plus you can adjust the length of pull) for different positions.
In a hunting situation having to adjust both every time to make a shot makes the chance of an
error greater in my opinion. At matches it makes very little difference if a person is proficient
at doing it.
If a person is use to canting and is aware of the effect, It is there choice and can as you said help
in other areas.
When hunting I have enough to do without adding another task to my check list and If I am
hunting uneven terrain I like to add a level to my scope also because it is harder to hold the rifle perfectly horizontal/level.
Just because it looks like it is level, just like Broz said ,it needs to be shot to be verified.
Just my opinion
J E CUSTOM
JE Custom. I understand your point. I'll have to go out to 1000 some time and compare poi for canted vs not. From what I was taught, the difference in poi should be within the value of 1 turret "click". I agree w your point about shooting w the scope level.
yawn
Well-Known Member
bil123, JE Custom is spot on and has explained it very well.
The 1/4 moa error at 1000 yds you talk of would only be the case if using something dead flat like a laser. But as you dial in elevation the error grows. The more you dial in the greater the error.
The 1/4 moa error at 1000 yds you talk of would only be the case if using something dead flat like a laser. But as you dial in elevation the error grows. The more you dial in the greater the error.
el matador
Well-Known Member
- Joined
- Jul 30, 2008
- Messages
- 647
Not exactly. This would be true if you're reticle is canted when shooting but not if the gun is canted and the reticle stays plumb. Having everything perfectly plumb and aligned is ideal, but canting the rifle for a more comfortable fit will only introduce a small amount of error, especially if you're zeroing at 200 or 300 yards. That 1/4" misalignment will equate to 2-1/4" at 1000 yards if you zero at 100 but will only throw you off 1" if you zero at 200. The most crucial alignment, as has been stated a few times already, is making the reticle plumb when you shoot. If your reticle is plumb when your scope level says it is you are good to go. I level my guns the best I can and then use a plumb bob to make sure the reticle is plumb. A piece of rope with a weight attached works great and can be easily seen from across the yard.bil123, JE Custom is spot on and has explained it very well.
The 1/4 moa error at 1000 yds you talk of would only be the case if using something dead flat like a laser. But as you dial in elevation the error grows. The more you dial in the greater the error.
yawn
Well-Known Member
Not exactly. This would be true if you're reticle is canted when shooting but not if the gun is canted and the reticle stays plumb. Having everything perfectly plumb and aligned is ideal, but canting the rifle for a more comfortable fit will only introduce a small amount of error, especially if you're zeroing at 200 or 300 yards. That 1/4" misalignment will equate to 2-1/4" at 1000 yards if you zero at 100 but will only throw you off 1" if you zero at 200. The most crucial alignment, as has been stated a few times already, is making the reticle plumb when you shoot. If your reticle is plumb when your scope level says it is you are good to go. I level my guns the best I can and then use a plumb bob to make sure the reticle is plumb. A piece of rope with a weight attached works great and can be easily seen from across the yard.
Ah yes you are quite right , I miss read the post and assumed reticle cant.
...will only introduce a small amount of error, especially if you're zeroing at 200 or 300 yards. That 1/4" misalignment will equate to 2-1/4" at 1000 yards if you zero at 100 but will only throw you off 1" if you zero at 200. The most crucial alignment, as has been stated a few times already, is making the reticle plumb when you shoot.
Excellent point. I forgot to mention that if you zero at a longer distance, it eats up some of the error.
J E Custom
Well-Known Member
I guess I am still confused as to why you would not want to eliminate as much error as possible.
The amount of error depends on the amount of cant. first, how can you measure a 1/4'' of cant
and the fact that the cross hairs /reticle are level, does not mean that there will not be any error
as elevation is added. The amount will vary but there will always be error if the rifle and the scope are not level with each other, and the scope and rifle combination is not level with the world
If the reticle and the rifle ARE true to each other and the rifle is canted there will error in Windage as the elevation is added (The reason for an additional scope level to assist in keeping everything level to minimize or eliminate horizontal error while increasing elevation.
The line of the bore and the line of the sight will always form a triangle. If held vertical, they will intersect at some point and beyond this point the dispersion will increase with distance, if the triangle is canted by any amount or means, the line of sight and the line of the bore will go off in different directions. And the father the distance, the farther apart they will be.
AGAIN, There is nothing wrong with canting the rifle, scope, or both as long as you can overcome the error and keep shot placement on. BUT why?
Reading Windage is a major factor in good long distance accuracy, and adding even a few inches to the possible error could be the difference in a good shot or a poor hit.
J E CUSTOM
The amount of error depends on the amount of cant. first, how can you measure a 1/4'' of cant
and the fact that the cross hairs /reticle are level, does not mean that there will not be any error
as elevation is added. The amount will vary but there will always be error if the rifle and the scope are not level with each other, and the scope and rifle combination is not level with the world
If the reticle and the rifle ARE true to each other and the rifle is canted there will error in Windage as the elevation is added (The reason for an additional scope level to assist in keeping everything level to minimize or eliminate horizontal error while increasing elevation.
The line of the bore and the line of the sight will always form a triangle. If held vertical, they will intersect at some point and beyond this point the dispersion will increase with distance, if the triangle is canted by any amount or means, the line of sight and the line of the bore will go off in different directions. And the father the distance, the farther apart they will be.
AGAIN, There is nothing wrong with canting the rifle, scope, or both as long as you can overcome the error and keep shot placement on. BUT why?
Reading Windage is a major factor in good long distance accuracy, and adding even a few inches to the possible error could be the difference in a good shot or a poor hit.
J E CUSTOM
J E CUSTOM
I agree that by adding cant you do introduce a small amount of error into your shooting system. You are also introducing error if you have a less than steady hold. Canting the rifle (for some of us) makes for a steadier hold. If the amount of error that you remove by making your hold more steady is greater than the amount you introduce with the "misalignment" of the bore to reticle center, then you win.
I measure the amount of cant by betting up my rifle on a bench with the scope level set level. I holding a small level from the center of the ocular and measure how far off the bore is. It's not exact, but its repeatable.
I agree that by adding cant you do introduce a small amount of error into your shooting system. You are also introducing error if you have a less than steady hold. Canting the rifle (for some of us) makes for a steadier hold. If the amount of error that you remove by making your hold more steady is greater than the amount you introduce with the "misalignment" of the bore to reticle center, then you win.
I measure the amount of cant by betting up my rifle on a bench with the scope level set level. I holding a small level from the center of the ocular and measure how far off the bore is. It's not exact, but its repeatable.
bruce_ventura
Well-Known Member
I couldn't agree more. Aside from wind and range estimation, there are four ballistic errors that can creep into long range shots:I guess I am still confused as to why you would not want to eliminate as much error as possible...
1. Canting error
2. Spin drift
3. Reticle misalignment to the bore
4. Coriolis effect
If we focus exclusively on the big one (canting error) and ignore the others because we assume they are small, we could get lucky and they could cancel each other out to some extent, or we could get unlucky and they could combine with each other to create a significant aiming error. The goal of long range shooting is to minimize them all, so that we're not relying on luck.
Coriolis is the only error that can't be eliminated ahead of time because we have to know where we are on the globe and what direction we're shooting. The rest of these errors are relatively easy to eliminate, so why not just zero them out and be done with it?
1. Canting error: eliminating canting error requires the use of a properly aligned anti-cant indicator.
2. Spin drift: eliminating spin drift error requires the use of a ballistic computer and knowledge of the bullet length and rifling twist rate.
3. Reticle misalignment to the bore: eliminating this error is easiest to do with a reticle alignment tool like the RingTrue tool from HighPowerOptics. Most other methods reduce but not necessarily eliminate the error. How small does this error need to be?
In practice, I think the goal is to get the reticle and/or elevation turret axis aligned to the rifle bore within 0.125", which is less than half of a ¼ MOA click at long range when the rifle is zeroed at 100 yds. That angular error would be too small to contribute to a significant aiming error regardless of what direction it was in. A 0.125" offset amounts to about 4 degrees of scope roll, depending on the height of the scope above the bore. An angle of 4 degrees is less than one minute of the clock, which is pretty difficult to gauge when looking at the scope from the rear of the receiver. Eyeballing it will not guarantee that you can get the alignment error that small.
For custom rifles with high quality barrels attached to receivers that have been trued, and rings that have a low lateral offset between the rail and ring axis, the use of a level on the rail followed by a level on the scope or a plumb bob down range should get the scope reticle or elevation axis within 0.125" of the bore.
What about factory rifles? I frequently see factory rifles with bent barrels or barrels installed crooked in the receiver. This is usually the case when a scope needs a lot of windage adjustment to zero the rifle at 100 yds. Many rifle manufacturers know that these issues don't cause large dispersion, so they stopped worrying about them. Most shooters don't know how much lateral offset there is in their rings, or whether the offset is left or right. These are cases where a reticle alignment tool like the RingTrue tool is going to give perfect results, whereas the use of a level on the receiver and the scope could easily lead to an aiming error in an unknown direction.
