Shimming for moa

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I suppose you could measure it out, but I think it would be easier to just mark 20 MOA on a target at some distance. Point the scope at the top point, then tilt the scope until you are at the point 20 MOA lower. Then lock in the ring adjustments. That basically what I did when I just got aset of adjustable Eagle Vision rings. I don't think it needs to be too scientific.
 
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Today, I am asking myself the same question, am at 100 yards, and about to try to go to 200 yards. Have the FX No Limit adjustable scope mounts. Targets and chrono are coming soon. The trajectory calculator, 2" sight line above barrel. approx 850 to 900fps fps, 25 gr slug, 110 bar, position 3 on wheel, and medium on flow, Crown 700mm. trajectory says from 50 yd to 100 yard = 4" to 5 ", but the 100 yd to 200 yard is an additional approx 22 ".
Guessing that with that much vertical drop, I need to max out the adj FX scope rings, for the first try.
Or what Ctshooter just said and measure 20 inches on target at 100 yards. In my case I am maxing out at my highest vertical limit of adjustment at 100 yards, so I hope the adj scope rings go a bit more, so I can bring it down a bit.
Going to attempt to be able to adjust scope only for 50 yard, 100 yard, and 200 yard. Count the available vertical clicks, 1/8 moa scope.

ShootersCalculator.com | Ballistic Trajectory Calculator

Calculates the ballistic trajectory of a bullet fired from a rifle, handgun or other firearm. Produces a ballistic trajectory chart and table that shows the drop, velocity, kinetic energy, windage, and trajectory of a bullet.
shooterscalculator.com shooterscalculator.com
 
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cavedweller said:
This question pertains to scope rings that allow you to adjust for elevation.
How much lift / space would you need in the back scope ring to equal 20 MOA? A tooth pick or ? I’m sure there is math involved?🙄
In the olden days B4 adjustable Rings, people shimmed scopes.
Click to expand...
I'm so weak on math that I'm not sure if the two postings below are correct. I just shoot and adjust. I never measured to confirm.

WestHunter Adjustable Scope Rings - Formula to calculate how much they adjust

Hello everyone. I wanted to "reach out" with my 2240, so I had to know how much adjustment I had on my turrets. This gun has a Hawke Vantage 4-16x50 scope that has an elevation turret range of 80MOA, or 320 clicks. My gun was zeroed at 50 yards, and it ended up being 239 clicks, or 59.75MOA...
www.airgunnation.com www.airgunnation.com

FX no limits or any adjustable type of scope ring/mount

I’m curious to know approximately how much do you all choose to raise the rear end of an adjustable scope ring/mount to achieve what you want in achieving lots of elevation turret dialing. Are you typically just after the 20 MOA which is only a strong 1/32” rise(for 100 yards, and a distance of...
www.airgunnation.com www.airgunnation.com
 
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The calculation is a pretty simple matter of scaling one dimension to another. Let's say my rings are 3 inches apart and I'm shimming by 20 thousandths of an inch. If I want to know how much it alters the point of aim at 50 yards, I calculate how many times 3 inches will go into 50 yards. Then multiply that number by the 20 thousandths.

I put it into a simple spreadsheet. Following is a link to download a copy, and a screenshot.

Dropbox

www.dropbox.com www.dropbox.com
scope ring compensation.gif
 
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What I usually do, in order to give myself the maximum flexibility to DIAL my yardages, is to:

Set the elevation turret 1/2 turn up from the bottom.
Use the adjustable rings to get the elevation zero'd at 50 yards.
Tighten up the adjustable feature on the rings.

This will give you the maximum upward elevation for shooting longer ranges with your air rifle. For example, I can dial to about 330 yards with my .25 Panthera 600mm and Athlon Midas BTR gen2 4.5-27x scope shooting Altaros 49.5 grain ATP Smooth slugs at 885 fps...
 
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nervoustrig said:
The calculation is a pretty simple matter of scaling one dimension to another. Let's say my rings are 3 inches apart and I'm shimming by 20 thousandths of an inch. If I want to know how much it alters the point of aim at 50 yards, I calculate how many times 3 inches will go into 50 yards. Then multiply that number by the 20 thousandths.

I put it into a simple spreadsheet. Following is a link to download a copy, and a screenshot.

Dropbox

www.dropbox.com www.dropbox.com
View attachment 362384
Click to expand...
Damn!
 
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nervoustrig said:
The calculation is a pretty simple matter of scaling one dimension to another. Let's say my rings are 3 inches apart and I'm shimming by 20 thousandths of an inch. If I want to know how much it alters the point of aim at 50 yards, I calculate how many times 3 inches will go into 50 yards. Then multiply that number by the 20 thousandths.

I put it into a simple spreadsheet. Following is a link to download a copy, and a screenshot.

Dropbox

www.dropbox.com www.dropbox.com
View attachment 362384
Click to expand...
I was actually looking for something like this before getting adjustable rings haha.
 
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Usually when I install a MIL scope, I set it up with adjustable rings (or shims) so that it is zero'd at 50 yards with the elevation turret 1/2 turn from the bottom. I actually just did this again with my .25 Panthera 600mm and 4.5-29x Athlon Cronus scope. In this configuration, I can dial out to in excess of 350 yards, which is about as far as I need to go, even for X matches. This is with the Altaros ATP Smooth 49.5 grain slugs at 885 fps.
 
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Want to make it even easier so you don't have to use the math except to check my work?

use 3.44 inches. if you use dovetail this is easy. use the front edge of the scope ring as the hinge point.

use this as hpt.jpg


Slide the front of the rear scope ring 3.44 inches back.

set as 3,44.jpg


now when you want to raise the rear 20 MOA you put a feeler gauge .020 right at the front edge of the rear scope ring adjustment while making sure the front edge for the front scope ring stays all the way down. lock everything down and remove the feeler gauge. Want 40MOA? stack enough feeler gauge shims to get 0.040 inches and so on.

feeler here.jpg


On the picantinny rail it is slightly different as the slots in the rail may not allow you to use the front edge. You can either grind the post flat that prevents you to slide the ring back and then slide the rear scope ring forward and back, or mark the scope ring.

3.44 inches.jpg


like this.

pic rail.jpg


then put the feeler gauge right at but no further forward than that line you just marked.

try it, check my math. Neat huh?

I used https://www.inchcalculator.com/isosceles-triangle-calculator/

60 MOA is 1 degree. So
30 MOA is 30/60 = 0.5 degree.
20 MOA IS 20/60 = .3333333

Vertex Angle (β) is the angle you want in degrees

Side 'a' is 3.44

'b' is the feeler gauge thickness


Allen
 
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