Scope base/mount MOA calculations

Rob01 said:

Scope internal elevation not specified? It's specified in every spec sheet I have seen. It's not hard to figure out. Figuire your scopes travel, how much elebvation you need to reach the max distance you will shoot your cartridge of choice and then figure what canted base you can use. That easy.

And not sure what that whole "zeroing" chart is about but you zero at 100. Having a different base doesn't change that.

Click to expand...

Hi Rob01

Thank you for the reply,

For example I have a Leupold Mark 5 HD 5-25x56,
According Leupold : Elevation Adjustment Range is 35 Mil,Range of the elevation ring is 30,5 MILS, not total internal elevation of the erector, that’s why you can adjust the zeroing of your scope.

According to a review made by BigJimFish:

« Leupold lists the Mark 5HD 5-25×56 as having 35mil for travel in its elevation. This is doubly incorrect. The elevation knob will go just 3 turns at 10mils / turn for 30mils exactly from the zero stop and has just .5mil below the stop, so, in use, you do not get 35 mils. In case you are thinking that total internal travel is 35 mils, that is also not correct. I measured 43.7 mils of total internal travel, so no part of its travel is 35mils. However, you are very likely to get the full 30 mils of travel on the elevation knob as its massive internal travel gives you a little leeway as far as canted bases go »

The actual elevation is 43,7 MIL

You can check this on your scope when you reach elevation limit:
If you have full windage available you are still in the rectangle elevation/windage
If you haven’t full windage available, you have reached the elevation circle limit.

The main problem is to stay in a full windage availability and good optical quality regarding the distances you shoot generally. For few long distances shoots you can accept to approach optical limits.
For example, I want to stay in the green zone for my 90% shots, I can accept to be in Yellow or Orange zone for the zeroing and for the 10% longest shots. (All values in the sheet are theoretical because I haven’t the real values nor the real knowledge of the scope.

For example, I don’t know if the full erector travel is symmetrical or not regarding the center of the optic,
With a centered travel, the ideal base/mount value would be 50 MOA base/mount on the Leupold Mark 5 HD 5-25x56.

Thank you Rob01 !

I am not trying to reinvent the wheel, but to understand scope capabilties and avoid multiple purchases of mounts / bases.

Habu34

PS: Example of mount/base problem


« I am running a 60 MOA base on the Vudoo Gun Works V-22 with the ZC527.
My goal for this is to maximize the amount of elevation available on my .22LR rifle so I can get a 25 yard zero and still reach out to distance without needing to hold-over / hold-above.

After sighting in the scope and setting the zero stop for 25 yards, I have 31.3 MIL adjustment available to me which should get me well over 500 yards before I need to hold above target.

I did try the 60 MOA base on my V-22 with the Kahles K525i but I literally needed to bottom out the elevation turret in order to get a 25 yard zero leaving no room on the bottom end for any deviation due to atmospheric or other environmental changes. »

Another explanation of problem by Vector Optics :

Why Can't Your Scope Adjustment Go Straight​

September 04th, 2020

Evelyn: Hey, Stephen, there is a problem bothering me recently. When I adjust the scope windage or elevation, it won’t go straight but go diagonally. What’s the problem of my scope?

Stephen: In fact, it does not go diagonally but go in an ARC. To solve this problem, you need to know how the scope adjustments work.

Evelyn: That’s great!

Stephen: Just as Picture 1 shows, inside the scope is another tube, we call it erector tube which carries the reticle.
Around the erector tube are three connection points, they help to hold the erector tube. Two of them are windage turret and elevation turret respectively, the other one is called return spring or erector spring.



Evelyn: Oh, I don’t even know there is an inner tube inside the scope. So how dose it work?

Stephen: Let’s still refer to Picture 1, when we adjust the turrets to alter the position of the reticle, the windage turret or elevation turret push the erector tube to move to the target position.
Adjust the elevation turret, it pushes the erector tube up and down; Adjust the windage turret, it pushes the erector tube side to side.

Evelyn: I see. Now is the time to tell me why it goes in an arc.

Stephen: OK. Take the GIF Picture in the comment as an example.

Firstly, the windage has been keeping adjusted to far left or close to its extreme position;

Secondly, the elevation has been keeping adjusted up;

Finally, the erector tube comes to meet the inwall of the scope body.

At this time, if you continue to adjust the elevation upwards, the erector tube will walk along the shape of the scope inwall in an arc route.



Evelyn: Oh! I got it! It’s because there is no room for the erector tube to go up straightly!

Stephen: Yes! So some scopes limit the windage adjustment turret range to make sure there are enough room for erector tube to travel up and down straightly.
Go back to your problem, what you need to do is remember not to adjust the turrets too far or close to its extreme position.

Evelyn: Ah，it make sense！Thank you for your explanation. I’m going to readjust my scope!

Hello from France

I have just received directly from Zero Compromise Optic two screenshots regarding ZC527 / ZC420 scope ballistic possibilities with two calibers and different combinaison of base/mount from 0 Moa to 60 Moa.
Thank you Zero Compromise Optic.


Regards

Habu34