So I picked up a. RPR, 6.5 cm, threw a tango4 6-24x50 on it, got her zeroed. Went to check my elevation adjustment and can only dial up 8 mils. Full range is 15, the RPR has a 20moa base so shouldn't I have more room room for adjustment?
Rifle Scopes Zero/ scope help.
- Thread starter PhOnEpHrEaK
- Start date
One would think you would have about 11 mils of up elevation left unless your mount/rings are out of joint.
Are you using a cantilever mount? I've seen those be an issue sometimes.
Have you tried resetting the zero stop? That adjustment may be getting in your way.
Are you using a cantilever mount? I've seen those be an issue sometimes.
Have you tried resetting the zero stop? That adjustment may be getting in your way.
Check zero stop, and or you need a new base for your scope like a 30 MOA base
My wife thinks I only have 3 guns
My wife thinks I only have 3 guns
First time using a scope that actually has a zero stop in it, so any tips here? I used the books instructions to reset it, but something seems off here.
The rail base is the 20moa that comes on the RPR. The rings are Mk4s.
The rail base is the 20moa that comes on the RPR. The rings are Mk4s.
PhOnEpHrEaK, determine how much left and right windage you have available counting from your current zero. If when you adjusted for your zero you had to use a lot of windage adjustment it can severely limit the amount of vertical adjustment you have remaining.
In a perfectly centered reticle you would have max up, down, left, right adjustment to each edge of the circle. Now move crosshairs left or right and you will not be able to go up or down as much before hitting the edge of the circle. In simplistic terms this is how your vertical erector travel can be restricted due to windage adjustment. Many rifles do not have the front and back rail screws perfectly aligned and require excessive windage to correct, thereby introducing this type of error.
Just something else to check.
In a perfectly centered reticle you would have max up, down, left, right adjustment to each edge of the circle. Now move crosshairs left or right and you will not be able to go up or down as much before hitting the edge of the circle. In simplistic terms this is how your vertical erector travel can be restricted due to windage adjustment. Many rifles do not have the front and back rail screws perfectly aligned and require excessive windage to correct, thereby introducing this type of error.
Just something else to check.
Alright, I disengaged the zero stop and tested the turrets. I have 16.5 mils from top to bottom, book states it should have 15.
The scope is mounted in mk4 superhighway rings, on the 20 moa base that comes on the RPR.
Pell I almost have 7 mils right and 5 mils left.
The scope is mounted in mk4 superhighway rings, on the 20 moa base that comes on the RPR.
Pell I almost have 7 mils right and 5 mils left.
Well, something is still off somewhere and here is what I think is happening to you.
Doing a quick calculation using the book numbers of 15 mils total elevation and windage adjustment you should theoretically get 7-1/2 mils "Up, Down, Left, Right" adjustments assuming you were able to get zeroed on the optical center of the scope. This rarely happens and it definitively has not happened in your case.
A 20 MOA base lowers the front of the scope by an angular dimension of about 5.8 mils and requires the turrets to be adjusted by 5.8 mils to maintain your original zero or aimpoint. Note that your scope still has 15 mils of total elevation travel, but now, instead of looking at your target through the center of its total travel, you are looking through it at a location that has been shifted by 5.8 mils along the vertical line. In theory, you will now have (7.5 + 5.8) = 13.3 mils of "Up" correction, and (7.5 - 5.8) = 1.7 mils of "Down" correction. Still a combined total of 15 mils!
Because you can only dial up 8 mils instead of 13.3 mils, assuming your scope is working correctly, implies that your mounting system is requiring your scope be adjusted by about 5.3 mils in elevation to be zeroed, which is unfortunately eating up almost all of your 20 MOA (5.8 mil) base.
Your windage adjustment looks to be about 2 mils off optical center and the travel restriction of 12 mils total instead of 15 mil optimum travel is consistent with the elevation issues being observed as the farther from optical center, the greater the turret travel restriction.
Seems like the rail/rings may be misaligned on your RPR or the scope has a turret/reticle centering issue. Neither is a pretty solution.
Some questions to consider in troubleshooting:
Have you ever had another scope mounted on this rifle? Did you use the same rings? Did you have any issues with adjusting zero?
Conversely, have you ever had the Tango scope mounted on anything else? Any issues with alignment when setting zero?
Good luck!
Doing a quick calculation using the book numbers of 15 mils total elevation and windage adjustment you should theoretically get 7-1/2 mils "Up, Down, Left, Right" adjustments assuming you were able to get zeroed on the optical center of the scope. This rarely happens and it definitively has not happened in your case.
A 20 MOA base lowers the front of the scope by an angular dimension of about 5.8 mils and requires the turrets to be adjusted by 5.8 mils to maintain your original zero or aimpoint. Note that your scope still has 15 mils of total elevation travel, but now, instead of looking at your target through the center of its total travel, you are looking through it at a location that has been shifted by 5.8 mils along the vertical line. In theory, you will now have (7.5 + 5.8) = 13.3 mils of "Up" correction, and (7.5 - 5.8) = 1.7 mils of "Down" correction. Still a combined total of 15 mils!
Because you can only dial up 8 mils instead of 13.3 mils, assuming your scope is working correctly, implies that your mounting system is requiring your scope be adjusted by about 5.3 mils in elevation to be zeroed, which is unfortunately eating up almost all of your 20 MOA (5.8 mil) base.
Your windage adjustment looks to be about 2 mils off optical center and the travel restriction of 12 mils total instead of 15 mil optimum travel is consistent with the elevation issues being observed as the farther from optical center, the greater the turret travel restriction.
Seems like the rail/rings may be misaligned on your RPR or the scope has a turret/reticle centering issue. Neither is a pretty solution.
Some questions to consider in troubleshooting:
Have you ever had another scope mounted on this rifle? Did you use the same rings? Did you have any issues with adjusting zero?
Conversely, have you ever had the Tango scope mounted on anything else? Any issues with alignment when setting zero?
Good luck!
So last night I pulled the scope, rings, and base. I measured the base and rings and they seem to be good. That tells me that the problem is the scope or the rifle. Possibly the holes are drilled off center?
I haven't tried to mount the scope on another rifle yet. I may pull the mk4 off of my 308 and swap scopes just to see.
When I get home tonight I will double check my numbers but I'm sure I had 16.5 mils of elevation, and only 12.5 of windage; hopefully the scope isn't out of spec like it seems.
Pell, thank you for taking your time to help me with this issue.
I haven't tried to mount the scope on another rifle yet. I may pull the mk4 off of my 308 and swap scopes just to see.
When I get home tonight I will double check my numbers but I'm sure I had 16.5 mils of elevation, and only 12.5 of windage; hopefully the scope isn't out of spec like it seems.
Pell, thank you for taking your time to help me with this issue.
Happy to help! Your scope may be just fine! It is just showing symptoms associated with having to make large corrections to get it to zero due to rail misalignment. If scope is zeroed significantly off the optical center, turret travel may be significantly reduced from design specifications.
Obviously, if you were to mount another scope on the rifle and it too needs large corrections to zero, then you know the issue is the mount setup on the rifle and not your scope.
If rifle screws are drilled off center and/or with the wrong offset between them, the stress put on the rail can bend or twist it and could well be the source of your problems. Once you can confirm it is a mounting and not a scope problem, you might try loosening the rail and see if its bottom sits flat on the receiver and if the screw holes align well with rail. Might be good to try the front and back screws by themselves to see how it naturally mates with the receiver. Also check the distance between the screw holes and verify they align with the rail holes. If they are off by a small amount a gunsmith may be able to drill and tap oversize screws to correct the misalignment. Once again, good luck!
Obviously, if you were to mount another scope on the rifle and it too needs large corrections to zero, then you know the issue is the mount setup on the rifle and not your scope.
If rifle screws are drilled off center and/or with the wrong offset between them, the stress put on the rail can bend or twist it and could well be the source of your problems. Once you can confirm it is a mounting and not a scope problem, you might try loosening the rail and see if its bottom sits flat on the receiver and if the screw holes align well with rail. Might be good to try the front and back screws by themselves to see how it naturally mates with the receiver. Also check the distance between the screw holes and verify they align with the rail holes. If they are off by a small amount a gunsmith may be able to drill and tap oversize screws to correct the misalignment. Once again, good luck!
So I took the scope off as well as the base. mounted and remounted. I measured the base it seemed in spec. Where the action is drilled for the base seems slightly off to the right, and the rail feels/looks like it drifts that way.
However.. I remounted the scope and zeroed at 100 again. Once again I am right around that 8mil mark of elevation... the windage I have exactly 5 left and 10 right.
However.. I remounted the scope and zeroed at 100 again. Once again I am right around that 8mil mark of elevation... the windage I have exactly 5 left and 10 right.
Sorry PhOnEpHrEaK, Only suggestions I have left are to take the rail off and loosely put in only the rear screw. Next, tighten the rear screw on the base (no need to tighten all the way) and check to see if the front side starts to lift at all. Follow the same procedure using only the front screw. If the opposite side lifts in either case (or both), then stress is being introduced due to either a bent rail or a high spot on the top of the receiver. While off, confirm the rail is straight using a metal straight edge.
You can address the left/right rail misalignment by having a gunsmith re-align the screw centers on the receiver and tap with oversize screws.
If rail is bent, obvious fix is to replace the rail. If receiver has a hump or high spot, then you may need to bed the rail once the screw centers have been corrected.
Alternatively, you can call Ruger and see what they recommend based on your findings.
You can address the left/right rail misalignment by having a gunsmith re-align the screw centers on the receiver and tap with oversize screws.
If rail is bent, obvious fix is to replace the rail. If receiver has a hump or high spot, then you may need to bed the rail once the screw centers have been corrected.
Alternatively, you can call Ruger and see what they recommend based on your findings.
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