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Using the MOA

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 11:07
shooter4 View Drop Down
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Gentlemen.
Im heading for the range this weekend. I´ll be testing my scope/rifle from 100-400 yards. Yippee
I´ll be shooting .243 (100 grain bullets). My limited experience is with .22 cal where I have adjusted on range just by tilting the gun with satisfactory results. Now I want to really learn to use my 1/4" scope knobs. Problem is Im not 100% sure how much to turn from "zero" when the ranges get longer and wind (eg 10mph) starts to have effect.
Ive asked around and have gotten very unclear response. I wonder if shooters generally think about this?  Bucky
 
Is there anyone with enough experience here to get me in the ballpark and perhaps help me fill in here below?? Im a bit confused about how many "clicks" to use on different ranges to get the correct MOA. (guess I sound stupid - but what the hell, I just want to learn how to use my equipment properly).
 
Distance   -   Drop   -    MOA(clicks)    -    Wind drift   -   MOA (clicks)     
100          -       0      -       0      (0)       
200
300
400
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 11:43
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Here you go... 1MOA is 4 clicks.
You will need to calculate your own ballistics and verify.  http://www.eskimo.com/~jbm/cgi-bin/jbmtraj_simp-5.0.cgi



Edited by Kickboxer - February/27/2009 at 11:44
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 15:01
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The JBM calculator is a good one. Here's a sample for .243. I just plugged in a Hornady 100 gr. SPBT, which has a published BC of .405 and a muzzle velocity of 3000fps. If you're shooting commercial ammo, you can usually find out what those figures are, but be aware they are for a particular barrel and barrel length. Only a chronograph can tell you for sure.

Note that there are some factors that can change things. For instance, changing altitude and temperature to 6000 and 40F, respectively, will cause the bullet to land almost 2" higher @ 400 yards. I usually make sure to zero out target speed too. You can also use whatever units you want for drop and windage clicks from the pulldown. In this case, I selected 1/4 MOA.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 15:03
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Fantastic. This will get me in the ballpark with my 100 grain bullet. Now - am I understanding the usage of the click adjustments (in red) correctly?  What you say?

Distance   -   Drop   -    MOA(clicks)    -    Wind drift   -   MOA (clicks)     
100          -       0      -       0      (0)                 
200          -      2.6          1.2  (5 clicks)         1.2                 0.6  (2 clicks)
300          -      9.9          3.1  (13 clicks)       3.7                 1.2   (5 clicks)
400          -      22.5        5.4  (22 clicks)      7.7                 1.8  (7 clicks)
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 15:15
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One annoyance of JBM's otherwise excellent calculator is that it doesn't round off the number of clicks. It's not like you can dial in 5.8 clicks, for instance, when using the 1/4 MOA setting. You've got the right idea. Note that between the chart Kickboxer generated and mine there is not much difference in trajectories out to 300 yards, despite different BCs and muzzle velocities. Beyond 400 and especially when you get out to ranges past 500 there will be a significant difference between these rough values and more precisely measured data. And of course it all has to be verified with some real shooting.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 15:25
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Roger that.  That is great info and Im getting it (slowly :).  I think this education is gona help me get a better control of my shooting. Bunch of thanks.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 15:48
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You will have to experiment with how you want to handle the fractions, but you are in the ballpark for sure.  Have fun.  

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 16:41
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Will do. This table is of great help to get me in the ballpark, especially having the drop PLUS the clicks. Do you know where I can find similar table for 22LR bullets?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/27/2009 at 17:25
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Well, lessee: .22 LR has a BC probably not much better than a badminton birdie, so let's say .150 BC and 1280fps on a 38 gr. Remington round. So with a 50-yard zero, you'd get a 5" drop @100 (though it seems like mine only shoots 2-3" lower there), 40" @ 200 and 117" @ 300. You know, I still take the warning seriously that these little puppies can travel up to 1/2 a mile. But in practice a stray .22 round isn't likely to stay airborne very long...more like 1/7th of a mile over level ground.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/20/2009 at 21:39
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Originally posted by jonoMT jonoMT wrote:

One annoyance of JBM's otherwise excellent calculator is that it doesn't round off the number of clicks. It's not like you can dial in 5.8 clicks...


It does as of today. There is a checkbox at the bottom of the input pages that allows you to round to the nearest whole number.

I would have done it earlier, but I didn't know anybody wanted it...

Thanks!

Brad

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JBM Small Arms Ballistics -- http://www.eskimo.com/~jbm
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/20/2009 at 22:28
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