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Old 06-26-2019, 09:16 PM
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Setting scope for long distance shooting



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Explanations of minute of angle confused the heck out of me .
Here’s what I do .
I know using an ammo trajectory chart that SV ammo when sighted in at 50 yards , drops 7.5” at 100 yards .
My scope has 1/4” @ 100 yard clicks . So I multiply 4X7.5 = 30 clicks
HV ammo drops 4.5” @ 100 , so 4X4.5 = 18 clicks
So what’s the difference in what I’m doing and someone using minute of angle calculations? Why complicate things ?
Kirby

Last edited by kirby999; 06-26-2019 at 10:24 PM.
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Old 06-26-2019, 10:26 PM
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You're cheating.

Well, only sorta kinda, because you're only working at 100 yards and because one minute of angle is usually rounded to 1" at 100 yards so it all works out the same. That's not exact but it's so close that the rounding error doesn't matter.

So, riddle me this.... how much would you need to adjust if you were shooting at, say, 150 yards? Or 200 yards? That's where MOA comes in.

Let's say your drop at 150 yards is 16.5 inches down from your HV zero at 50 yards. How many clicks do you need to adjust to get on target? Your 1/4" clicks at 100 yards aren't 1/4" at 150 yards, eh? So you can't multiply 16.5 inches by four to get the number of clicks needed to get on target. How many would it take? Time's up! (42 clicks)

If you are working in MOA, however, it's easy math since your 1/4" at 100 yards clicks are actually (more or less) 1/4 MOA clicks. So, in our example, let's say we know our trajectory in MOA instead of inches. We know that at 100 yards we have a drop of 4.5 MOA and that at 150 yards it is 10.4 MOA and at 200 yards it is 17.6 MOA. So our click count at 100 yards is 4.5*4=18 clicks and at 150 yards is 10.4*4= just over 41 clicks and at 200 yards is 17.6*4=just over 70 clicks.

MOA -- minute of arc (shooters say minute of angle for whatever reason) -- is an angular measure, not a linear measure. Draw an angle. Put four hash marks across to connect the two legs at different points -- one about halfway to represent 100 yards, one at the end to represent 200 yards, then marks in between to represent 50 yards and 150 yards.

The angle doesn't change so the distance between the two lines when expressed as an angle (MOA) doesn't change. What does change is the distance between the lines expressed as a linear measure... if our angle is one MOA wide it is one inch wide at 100 yards but only 1/2" wide at 50 yards, two inches wide at 200 yards, etc.

Since the value expressed in inches will change with distance you have to convert the 1/4 MOA clicks of your knobs to inches at that distance. You have to do math to first convert those inches to MOA at that distance so you know how many clicks to count (since they really represent ~1/4 MOA and not 1/4 inch). If you're only working at 100 yards it doesn't matter since MOA and inches are more or less equal at 100 yards... but only at 100 yards. If you're shooting at longer distances it's really easier to skip all the converting and just track your trajectory in MOA.

Let me know if that only confused you more and I'll try a different... er... angle.
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Last edited by Sophia; 06-26-2019 at 10:52 PM.
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Old 06-26-2019, 10:26 PM
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Got to thinking and really confused myself .
Scope is 1/4” at 100 yards , 1/8” at 50 ? , so would it be 1/2” at 200 yards ? kirby
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Old 06-26-2019, 10:29 PM
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You answered while I was typing .
Thanks Sophia , now to try and drill this stuff into this old man’s brain. Kirby
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Old 06-26-2019, 10:32 PM
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So, where do you find a MOA chart for 22lr SV ammo ? Kirby
Edit : Sophia , I’m copying and pasting your explanation in my Ipad’s Notes for reference and more study . Kirby

Last edited by kirby999; 06-26-2019 at 10:37 PM.
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Old 06-26-2019, 10:49 PM
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Quote:
Originally Posted by kirby999 View Post
So, where do you find a MOA chart for 22lr SV ammo ? Kirby
You can use a ballistic calculator and tell it to spit out the results in inches or MOA or mil or all of them at once. You have to know some inputs up front... MV, height of scope above bore, etc, and the best it is going to do is get you close so you can fine tune from there on the range. I like this one:

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

The simpler of the options on the main page:

http://www.jbmballistics.com/ballist...culators.shtml

If your load shows up in the library (first window) you can skip the other inputs in that block (they will be ignored) and move down to MV and work down from there. You can leave most things at their default setting... you'll recognize which ones you should change. The last couple of blocks are where you tell it you want inches, MOA, whatever, as your output.

I used 1350 fps as the MV of your HV ammo as an input to get the drop to line up as 4.5" at 100 yards.
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Last edited by Sophia; 06-26-2019 at 10:54 PM.
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Old 06-27-2019, 07:44 AM
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Sophie gave an excellent explanation to your question I really can't add anymore than just a couple of links of a ballistic chart of 22 lr ammo. To the left of the chart are more drop down charts of 22 war and 17 hmr if interested. Also there is a link providing a video to Sophies explanation as well.
https://www.mcarbo.com/22LR-Ballistics-Chart
https://www.youtube.com/watch?v=VA2PZBD5Tjg
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Old 07-04-2019, 05:28 PM
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Does using a 25 MOA (or whatever) base change the results when zeroed at 50 yards?

How would you find bore to scope height now that it's angled?
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Old 07-04-2019, 05:59 PM
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The 25 moa rail allows me to use my 8-32x44 scope from 25 to 250 yards.
I boresight at 50 yards and adjust the scope to poi and record the turret settings.
Then with a ballistics chart, I can adjust the crosshairs to any distance out to 250 yards.
Simply a matter of dialing the scope to fit the drop correction from the ballistic calculator.
Individual settings for specific ammo/wind/distance are recorded in my log for later reference.

Last edited by jaia; 07-04-2019 at 06:03 PM.
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Old 07-04-2019, 09:08 PM
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Quote:
Originally Posted by Tomiboy View Post
Does using a 25 MOA (or whatever) base change the results when zeroed at 50 yards?
If I understand the question correctly the answer is "no." The amount of drop remains the same. All the base is doing is changing where your knobs (and reticle) are going to be set when you get zeroed. Instead of the reticle being at or near the center of its adjustment range when zeroed at 50 yards it is going to be near the extreme of the elevation adjustment range. The benefit of this is that it gives you a lot more room for "up" adjustment when you start dialing in for the drop at long range.

For example, if your scope has a range of 40 MOA adjustment that means 20 MOA down from center and 20 MOA up from center. If you are zeroed at the center of the range you only have room for 20 MOA of adjustment for drop at long range....maybe not enough if you are shooting at a very long range. With 25 MOA (or whatever) base you move your 50 yard zero from the center of the adjustment range to the edge so now you have 40 MOA of room for adjustment. Actual numbers are going to vary, of course, since you may not get all the way to the extreme limit depending on how much you had to start with and how much you add externally with the base.

Quote:
How would you find bore to scope height now that it's angled?
The angle isn't going to make much of a difference but the actual height of the base might. Just measure from the center of the tube to the center of the bore (eyeballing it right at the ejection port).
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Last edited by Sophia; 07-04-2019 at 09:12 PM.
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Old 07-04-2019, 09:36 PM
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I don't worry about my scope height.
All I care about is the difference in drop from one distance to another.
Time of flight from muzzle to target and gravity determines drop.
Knowing the drop at 50 yards and the drop at 200 yards means all I have to do
is subtract to determine my scope adjustment from my 50 yard setting to 200 yards.
When using the calculator the scope height is set to zero, angle of barrel is zero,
input muzzle velocity and set the interval distance to 25 yards.
Result is the vertical drop for each interval from 0 yards to 500.

Last edited by jaia; 07-04-2019 at 09:43 PM.
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Old 07-05-2019, 01:36 PM
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Here is a chart that can start you off about the moa adjustments needed for HV and SV velocities at various distances. Of course there will always be variables but I find that this is a good starting point. I shoot 200 to 230 yards all the time with iron sights using high velocity ammo and find that on my rifle a 513T with a 27" barrel I need about 12.5 moa elevation adjustment for 100 yards at jumps to 42.5 moa at 200 yards with my redfield sights. On my 10/22 with a 16" barrel with a rifle scope and a Nikon monarch with BDC reticle I need about 22 moa adjustment on my scope, but I only use the bottom hash mark below the center cross hairs.

If adjustments for elevation will be a problem I recommend that you buy a scope that always gives you at a minimum 80 moa of elevation adjustment or buy one with bdc reticles. My Nikon with bdc reticle allows me to take my 22lr out to 350 yards out all the time but I use the very bottom of the hash marks and than adjust with the knobs.

Anyway here is a link to a drop chart that might get you started, hope this helps.

https://www.huntinggearguy.com/rimfi...lr-long-range/

Last edited by ms6852; 07-05-2019 at 01:38 PM.
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Old 07-05-2019, 02:54 PM
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If you were to optically center a scope on a 22lr, mounted about 1 3/4" above bore center, shooting standard velocity ammo, say 1070 FPS, where will it typically print on a target when your POA is a 50 yard target? I've never really paid attention to this with a new scope but as I recall it hits low, but can't remember how much

What happens with a 25 MOA rail? It would definitely be higher but how much? 12.5"??

I guess I'm wondering if a 25 MOA rail helps the scope to be closer to optically centered at 50 yards?
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Old 07-05-2019, 03:38 PM
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Supposing you had a scope zeroed for 50 yards with Midas+.
Then you installed a 25 moa rail under it and the only thing that changed was the 25 moa vertical.
If you tried that new setup at 50 yards you'd hit about 13 inches above your aimpoint.
The reason to use a 25 moa rail is to allow you to keep your turret adjustments in the middle of their range
when shooting at distances beyond 125 yards.

Last edited by jaia; 07-05-2019 at 03:44 PM.
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Old 07-06-2019, 02:45 PM
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Not to put too fine a point on it but 1 MOA is actually 1.047 so at 100 yards the commonly use 1 MOA is "about" an inch. The problem is the difference at 200 yards can be a bit of a bother. For example if the bullet drop is 60 inches and one were to use the usually accepted 1/2 inch per click at 200 yards (assuming 1/4" clicks) 60/.5=120 clicks of elevation. But using the actual MOA at 200 yards of 2.094, 60/.5235=114 clicks. (2.094/4=.5235 equals one click at 200 yards). That's a difference of a bit more than 3 inches.

I know it's confusing but as Sophia pointed out, ballistics calculators can usually give you drop in both inches and MOA. The problem with ballistic calculators you can't just rely on the advertised velocity because not every lot is the same and even if it were the velocity out of your rifle isn't going to be the same anyway. But at least the ballistic calculator should get you in the ballpark.

I don't know why scopes are marked 1/4" or 1/8". I guess the manufacturers assume 1. people only shoot at 100 yards or 2. the shooter ought to be smart enough to figure it out for themselves. I'm not sure any scope directions points out the difference of MOA versus 1 inch.
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