fiftybmg
Well-Known Member
http://www.ysterhout.net/docs/cant/index.html
Feedback welcome on any forseeable problems with this method.
Feedback welcome on any forseeable problems with this method.
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Another take on adjusting scope cant
- Thread starter fiftybmg
- Start date
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FearNoWind
Well-Known Member
The article says "Because the scope mounts are already fitted to the rifle, it's not necessary to find the vertical of the rifle itself, only to align the bore center and cross hair center to the plumb line"
If the rifle is canted and you align the center of the bore with a plumb line (not an incredibly accurate idea in its own right) and then align the verticle cross hair with the plumb line you will, when bringing the rifles stock back to its own verticle, have a canted scope image.
I do see some promise in the general theory, given that all elements are on the same plane, but it is (IMO) no more accurate a process (and somewhat more bothersome) than the method I have used throughout the years.
If the rifle is canted and you align the center of the bore with a plumb line (not an incredibly accurate idea in its own right) and then align the verticle cross hair with the plumb line you will, when bringing the rifles stock back to its own verticle, have a canted scope image.
I do see some promise in the general theory, given that all elements are on the same plane, but it is (IMO) no more accurate a process (and somewhat more bothersome) than the method I have used throughout the years.
fiftybmg
Well-Known Member
The scope mount is fixed. This is not about adjusting the mount.
Aligning the mounts to each other and the bore axis is it's own science.
If the bore center and vertical crosshair are on the same vertical from the beginning, it's mission accomplished, no adjustment necessary.
If the scope mounts are true, and rifle is canted in the vice, the bore center and cross-hair center will not be vertical.
If the rifle is canted in the vice, and the bore center and crosshair center are vertical, the scope mounts were not fitted correctly.
fiftybmg
Well-Known Member
For example, a side mounted scope can't use this method.
The vertical of the scope and the bore center are not in the same vertical plane.
If the mounts are offset to the bore axis, then you have a degree of side mounting, the best you can do is get the scope axis parallel to the bore axis, but you have to use another method.
The vertical of the scope and the bore center are not in the same vertical plane.
If the mounts are offset to the bore axis, then you have a degree of side mounting, the best you can do is get the scope axis parallel to the bore axis, but you have to use another method.
Mikecr
Well-Known Member
I like your out-of-the-box perspective here.
There is another critical attribute of system cant -> elevation adjustment plumb -vs- reticle plumb
For those who dial, a full elevation travel test is needed to validate and ensure the POA adjustments stay plumb. In this case, reticle cant itself is meaningless to vertical. And after all, we could be using a simple dot aimpoint rather than a crosshair. It just cannot be assumed that a given cross hair is actually square to click adjustments.
Also worth mentioning; it's important that a level used in the field is scope mounted(not rifle mounted), to indicate either proven plumb elevation adjustments, or cross hair plumb, or both(if lucky). One level, on the scope.
I shoot a plumb line while I shoot a box with my scopes. There is error to filter in this with inaccurate guns, so I don't do the test until load development is completed.
Your test removes shooting error, but keep in mind that guns do in fact shoot with 'error'. That is, a tuned barrel is actually throwing every shot, very consistently, where it happens to.
Consider a bit of barrel recoil(while bullet is still in the bore), and this makes it easier to understand the 'throwing' 'where it happens to' part of it.
Nothing near a laser..
Next time you shoot a tiny group, on the third shot, press your thumb against the action tang. You may observe a shot thrown from the pack. What of adjusted POA? Of adjusted cant?
They were always a part of shooting system tune.
There is another critical attribute of system cant -> elevation adjustment plumb -vs- reticle plumb
For those who dial, a full elevation travel test is needed to validate and ensure the POA adjustments stay plumb. In this case, reticle cant itself is meaningless to vertical. And after all, we could be using a simple dot aimpoint rather than a crosshair. It just cannot be assumed that a given cross hair is actually square to click adjustments.
Also worth mentioning; it's important that a level used in the field is scope mounted(not rifle mounted), to indicate either proven plumb elevation adjustments, or cross hair plumb, or both(if lucky). One level, on the scope.
I shoot a plumb line while I shoot a box with my scopes. There is error to filter in this with inaccurate guns, so I don't do the test until load development is completed.
Your test removes shooting error, but keep in mind that guns do in fact shoot with 'error'. That is, a tuned barrel is actually throwing every shot, very consistently, where it happens to.
Consider a bit of barrel recoil(while bullet is still in the bore), and this makes it easier to understand the 'throwing' 'where it happens to' part of it.
Nothing near a laser..
Next time you shoot a tiny group, on the third shot, press your thumb against the action tang. You may observe a shot thrown from the pack. What of adjusted POA? Of adjusted cant?
They were always a part of shooting system tune.
fiftybmg
Well-Known Member
Thanks for the feedback.
I did read up on one method described on this forum, of shooting at a mark on the plumb line at 100, then dialing the elevation up around 24 inches, and shooting to the same point of aim. That is the true test of scope cant, which I also plan to perform.
Being new to rifle shooting, I can shoot well enough from a rest to 100 meters now, my goal is to move to 200, with 300 as my ultimate goal.
The platform is up to it, I think, initial sighting in gave me overlapping holes at 50 meters. The limiting factor right now is between the trigger and the bench.
I did read up on one method described on this forum, of shooting at a mark on the plumb line at 100, then dialing the elevation up around 24 inches, and shooting to the same point of aim. That is the true test of scope cant, which I also plan to perform.
Being new to rifle shooting, I can shoot well enough from a rest to 100 meters now, my goal is to move to 200, with 300 as my ultimate goal.
The platform is up to it, I think, initial sighting in gave me overlapping holes at 50 meters. The limiting factor right now is between the trigger and the bench.
gohring3006
Well-Known Member
I have found, starting with a high quality bedded base, high quality rings and high quality optics and doing what Mikecr describes, always give good results.
Your method is interesting though.
I have ran into problems with cheap components. I'm a firm believer in quality rings.
Your method is interesting though.
I have ran into problems with cheap components. I'm a firm believer in quality rings.
