Question about using hash marks for hold off.

[Dave Way]

So my question has to do with scopes with hash marks or multiple aiming points. I have read where it is best to set up a scope where it is as close as possible to the center of the scopes adjustment range by using rails or shims. For example using a 20 or 30 MOA rail to set up a 1,000 yard rifle. My understanding is that this is more of a mechanical thing, keeping the turret adjustments from being too extreme to get zeroed.

My question has to do with something else but still deals with use of the scope and parallax. Does it increase the possibility of scope induced error if I’m using maybe a 10 MOA aiming point? If I’m not using the center aiming point, I just wonder if things like eye placement are even more critical as far as parallax error goes.

Thanks,
Dave.

 

[Ranger188]

@Turbulent Turtle

 

[Walt Krafft]

At the worst possible moment, I would use the wrong aiming point.

 

[ShtrRdy]

It shouldn't matter. You should do something like a "tall target test" to measure what your scope is giving you.

As for shiming the scope to get the windage centered - if your adjustment is all the way to one end there is something wrong that needs to get fixed.

 

[std7mag]

@ShtrRdy,

The OP didn't specify windage or elevation.
I'm leaning towards them meaning elevation though.

So my question has to do with scopes with hash marks or multiple aiming points. I have read where it is best to set up a scope where it is as close as possible to the center of the scopes adjustment range by using rails or shims. For example using a 20 or 30 MOA rail to set up a 1,000 yard rifle. My understanding is that this is more of a mechanical thing, keeping the turret adjustments from being too extreme to get zeroed.

My question has to do with something else but still deals with use of the scope and parallax. Does it increase the possibility of scope induced error if I’m using maybe a 10 MOA aiming point? If I’m not using the center aiming point, I just wonder if things like eye placement are even more critical as far as parallax error goes.

Thanks,
Dave.

Dave,

I usually run 20 MOA, one piece bases on all of the rifles that I can.
And if you're trying to shim the scope so that the elevation is centered again, you're not getting the point of using a base with built in MOA.
The whole point of using a 20 MOA (or 10, or 30) base is that it puts the travel to such a place as to allow you to dial up for further distances.
If you need yet more elevation than there is travel, you can use the holdovers.

 

[Kracken McGraw]

I assume on this that your eye optically centers the scope. Then when you move the rifle left or right to correct windage, your eyes center on the new hashmark that’s now in the center.

 

[Evan]

With both my Sightron and my GE, if I bottom the elevation adjustment out, I have to adjust my head some to get a full sight picture again. It is subtle but definitely there. So at the adjustment extreme, I think parallax is impacted. More in the middle of the range, I am not so sure there is a significant effect like that.

A hash mark that is 10 or 20 MOA is still, relatively speaking, near the center of the lens. I don’t think, but don’t know for certain just how much that might distort your point of aim.

 

[Dave Way]

With both my Sightron and my GE, if I bottom the elevation adjustment out, I have to adjust my head some to get a full sight picture again. It is subtle but definitely there. So at the adjustment extreme, I think parallax is impacted. More in the middle of the range, I am not so sure there is a significant effect like that.

A hash mark that is 10 or 20 MOA is still, relatively speaking, near the center of the lens. I don’t think, but don’t know for certain just how much that might distort your point of aim.

That’s what I’m wondering. Let’s make it extreme. Suppose the aiming point is at the very edge of the optical field of view. While using that as the aiming point is it easier to induce unwanted error? If it is, I would assume any deviation from using the very center of the field of view(cross hair, etc.) could contribute to a shift of impact point.

Dave.

 

[Dave Way]

@ShtrRdy,

The OP didn't specify windage or elevation.
I'm leaning towards them meaning elevation though.


Dave,

I usually run 20 MOA, one piece bases on all of the rifles that I can.
And if you're trying to shim the scope so that the elevation is centered again, you're not getting the point of using a base with built in MOA.
The whole point of using a 20 MOA (or 10, or 30) base is that it puts the travel to such a place as to allow you to dial up for further distances.
If you need yet more elevation than there is travel, you can use the holdovers.

I have 20 MOA rails on my rifles too. I only mentioned shims because I have heard of people using them. I haven’t but thanks for the response.

Dave.

 

[Dave Way]

I assume on this that your eye optically centers the scope. Then when you move the rifle left or right to correct windage, your eyes center on the new hashmark that’s now in the center.

But the hash mark is not in the center of the FOV at that point. Your eye has to be to get a full FOV. Thanks for the response.

 

[Turbulent Turtle]

So my question has to do with scopes with hash marks or multiple aiming points. I have read where it is best to set up a scope where it is as close as possible to the center of the scopes adjustment range by using rails or shims. For example using a 20 or 30 MOA rail to set up a 1,000 yard rifle. My understanding is that this is more of a mechanical thing, keeping the turret adjustments from being too extreme to get zeroed.

My question has to do with something else but still deals with use of the scope and parallax. Does it increase the possibility of scope induced error if I’m using maybe a 10 MOA aiming point? If I’m not using the center aiming point, I just wonder if things like eye placement are even more critical as far as parallax error goes.

Thanks,
Dave.

The reason I set my Majesta riflescope to be as near mechanical zero as possible at 1000 yards, is because that also coincides with the optical sweet spot and when these riflescopes that cost so much are on my rifle, I want the best IQ (image quality) possible.

Inside a riflescope, there is another tube called the erector tube that contains a number of lenses to flip and magnify the image. This image is presented to the eyepiece at the second focal plane. The front of this erector tube is what you move around with the adjustment turrets, when you are zeroing the riflescope. In front of the erector tube is the objective lens group, that big lens at the front of the riflescope that focuses the entire image of the objective at the first focal plane, at the front of the erector tube.

The very best IQ of that first focal plane image is in the center, that's how optics work. It doesn't mean the IQ at the edges of the lenses is bad, it just means it's the best in the center. In the olden days, the spring material used to perform the adjustments with the turrets, could take a set if compressed too much for too long. That issue is not really a concern these days, and certainly not with the alpha riflescopes. However, if you use up all the elevation to get to 1000 yards, you won't have any leeway if conditions change and you need an extra couple MOA. It also cuts down on the windage travel.

The gentleman who suggested always using a 20MOA ramp is not wrong. I actually have that on most of my rifles. It's only my match F-TR rifle with the Majesta, that I added more MOAs with Burris rings to get close to 32MOA at mechanical 0.

The image that gets transmitted to your eye is whatever the view of the front of the erector tube sees in the FFP. Whether you have an FFP or SFP reticle (or both), the location of the erector tube will not create any deviation on the reticle. However, that said, do not hesitate to verify the focus on your riflescope if you put in a massive amount of elevation after focusing. As a matter of fact, at higher magnifications, I am always tweaking the side focus as conditions change.

 

[dthomas]

Dave don't forget what turbulent turtle is doing is for f class as the rifle primarily only gets used at 1000 yards.

 

[Kracken McGraw]

But the hash mark is not in the center of the FOV at that point. Your eye has to be to get a full FOV. Thanks for the response.

I just pulled that answer out of my small pail of common sense, lol.
But in my mind let’s say you pull the rifle into the wind left one hashmark, wouldn’t your head or eyes adjust over right just a bit to line up with that hashmark that you are going to use?

 

[Dave Way]

Dave don't forget what turbulent turtle is doing is for f class as the rifle primarily only gets used at 1000 yards.

Most of my shooting is also at 1K. Thanks.

 

[SKWERLZ]

I run a 45moa rail on my main LR rifle.
Hash marks seem to be accurate throughout the scopes elevation range even at extreme edge of travel.

 

[Turbulent Turtle]

I run a 45moa rail on my main LR rifle.
Hash marks seem to be accurate throughout the scopes elevation range even at extreme edge of travel.

Of course they would. Nowadays, reticles are etched onto glass and once that's done, the hash marks don't move around on the glass. In an FFP design, the reticle is attached to the front of the erector tube, so it moves up and down and sideways with the rest of that end of the erector tube. in an SFP design the reticle is located at the rear of the erector tube and it stays put, on the front of the erector tube is moving.

Perhaps at some point, the reticles may be formed electronically so you could program your own reticle, and if you program it in Fortran, we could see hash marks moving around on their own, and that would be bad.

 

[ELR LVR]

What you are doing is using an MOA rail to get as much vertical adjustment out of your scope as possible
we never adjust our vertical BELOW 100 yards right?
so if we have our scope zeroed at 100 but still can adjust DOWN another 20 MOA
that is 20 wasted MOA we could use at long range
----------------------------------------------------------------
the next issue is windage
the most amount of windage available is when the scope adjustment is in the middle vertically
Ideally if you shoot mostly at 1000 yds, this is where you want to take advantage of the max amount of windage adjustment
as the scope nears its top vertical, the amount of windage becomes less and less available
so you would want your scope centered vertically at 1000 yds to have as much windage as possible at 1000 yds
Or close to that
if we did not use an MOA rail and adjusted up to 1000 yds, we may not have any windage adjustment left because it has decreased once topped out
(the top of a circle has less width than the center of the circle, and a scopes internals are still confined
within a circle)
--------------------------
If you ever shoot at 100 yds say for sight in or load testing etc
you dont want your scope to not be able to adjust vertically down to 100 yds
yet to have the max amount of windage at 1000 yds there may have to be a trade off
Such as being zeroed for 300 yds and you would have to hold "DOWN" to print at 100 yds
--------------------------
Usually with a 20 or even 30 MOA rail you can zero at 100 yds and have enough to reach 1000 yds
as for holdovers, that is a personal choice as opposed to dialing scope
yet as someone mentioned having your focus in the center is optimum
I dial scope to have my target focused in the center
unless the holdover is 1 mil or less, then I holdover since wind can change too fast
I dont want to have to constantly be dialing a click or two back and forth
I think the max amount of wind I have ever had to dial in for at 1000 yds is 2 Mils in a 20 mph wind
or 6 feet, well within the field of view of the scope

 

[6BRA]

Burris XTR signature rings with inserts. Will allow me to remove MOA from my 20 MOA base which is integral of the action. For short to midrange.

 

[SteveOak]

This thread alone is worth the cost of an annual membership.