Rifle Scopes Assistance for a math challenged shooter

Ballistic Archer

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May 30, 2011
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I attempted to work the caculations to figure out the CQ reticle conversions for myBurris MTAC 1-4X myself only confused myself further. Here is the ballistic data from JBM:


Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (Col 2) (in) (Col 2) (ft/s) (none) (ft•lbs) (s) (in) (Col 2)
0 -2.6 *** 0.0 *** 2205.5 1.975 1349.9 0.000 0.0 ***
50 -0.3 -1.2 0.3 1.3 2085.3 1.868 1206.7 0.070 12.3 47.0
100 -0.0 -0.0 1.4 2.7 1968.2 1.763 1075.0 0.144 25.3 48.4
150 -1.9 -2.4 3.3 4.1 1853.3 1.660 953.1 0.223 39.2 49.9
200 -6.4 -6.1 6.0 5.7 1742.9 1.561 843.0 0.306 53.9 51.4
250 -13.7 -10.5 9.6 7.4 1637.6 1.467 744.2 0.395 69.5 53.1
300 -24.3 -15.4 14.3 9.1 1533.9 1.374 653.0 0.489 86.1 54.8
350 -38.5 -21.0 20.1 11.0 1434.8 1.285 571.3 0.591 103.9 56.7
400 -57.0 -27.2 27.2 13.0 1343.6 1.203 501.0 0.699 123.0 58.7
450 -80.3 -34.1 35.5 15.1 1261.3 1.130 441.5 0.814 143.2 60.8
500 -109.1 -41.7 45.1 17.2 1189.0 1.065 392.3 0.936 164.8 63.0
550 -144.0 -50.0 56.0 19.4 1127.4 1.010 352.7 1.066 187.6 65.2
600 -185.7 -59.1 68.0 21.6 1076.2 0.964 321.4 1.202 211.6 67.4
650 -235.0 -69.0 81.1 23.8 1033.6 0.926 296.5 1.345 236.7 69.5
700 -292.4 -79.8 95.1 26.0 997.4 0.893 276.1 1.493 262.7 71.7

31/03/13 15:43, JBM/jbmtraj-5.1.cgi

The Burris CQ reticle corrections (MOA) are:

Center Dot- 100 yd zero no correction
Dot #2- -3.3
Dot #3- -6.1
Dot #4- -9.6
Dot #5- -13.6

Can one of you pros who are much better at math calculate the yardages of the CQ dots for my .300 balckout data above? (and perhaps post the formula for doing so, in case I will be able to comprehend it....)

I hate to ask, balancing a checkbook is about the extent of my math capability. God gave me height and good hands, not and abundance of math talent...

So, I therefore humble myself to you guys smarter than myself. Feel free to bust my balls if you like, we cant all be math gurus.

BA

PS- FYI, the little AAC/Remington Model Seven .300 BLK averages .71" at 100 yds with the Remington Premier Match 125gr OTM at 4X from a bipod, just in case you were curious what I was using.

Thanks gents.
 
Last edited:

runngun

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Oct 25, 2008
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Aberdeen Proving Ground, MD
You need to run the JMB calculations again, but this time have it output drop in MOA for column 2. Leave the number for column 2 as "1". Then compare and see what distance has a drop in MOA that matches your dots in your scope.

Update: it looks like you have the drop in .5 MOA so
Dot 2 is 210
Dot 3 is 275
Dot 4 is 335
Dot 5 is 400

When you run it again also change the range increments to 5 yards and it will be a lot more accurate. I was just aproximating based on the given info.
 
Last edited:

BobinNC

Gunny Sergeant
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Jan 31, 2009
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Goldsboro, NC
Dot #2 = 195 yds
Dot #3 = 258 yds
Dot #4 = 324 yds
Dot #5 = 389 yds.

Assuming: of course the velocity is really 2205 FPS and that Burris's published Reticle Corrections are near correct, and your at sea level, and your scope height is 1.8".

Change any assumption and your ranges will change. Drops should be confirmed by actually shooting them...


No math needed, I just ran JBM in MOA, with 5 yd increments, with the data you provided above and compared the data to the MOA reticle corrections you gave above.....
 

Ballistic Archer

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May 30, 2011
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Thanks guys, the data I entered is chornographed and accurate, I know how to collect data just not so good at using it I guess..... Bullet is 125 gr .308 OTM.338 BC, 2200.7 FPS, sight height 2.65" center of bore to center of scope tube, temp was 54 degrees.

This was the first time I used JBM, its very nicely done and more detailed than the calculator I was using. For my Nikon scopes I was using the Spot On system, that worked very well, but I got a bad computer virus from it. I will confirm the the yardages, but I am really trying to conserve .300 blackout ammo, especially the premier match, since all .300 is hard to find and, I dont have time to do hand loading/testing much right now. If I have the dots worked out I can laser set some targets with my rangefinder at those distances and confirm. (My usual technique)

Thanks very much guys, I will run it again, if one of you boys feels like checking me by running it with my above data please do.

Again, thanks from the algebra deficent trigger puller on the site.

BA
 

Ballistic Archer

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May 30, 2011
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North East USA
Reset the data and ran it again in 5yds, you were very close:

I got 205, 270, 335 and 400 for the 125gr OTM. So, it only varied on the first dot 5 yards.

Thanks for getting me straight on how to use JBM, I plan to check my other cards with this as well.

BA

You need to run the JMB calculations again, but this time have it output drop in MOA for column 2. Leave the number for column 2 as "1". Then compare and see what distance has a drop in MOA that matches your dots in your scope.

Update: it looks like you have the drop in .5 MOA so
Dot 2 is 210
Dot 3 is 275
Dot 4 is 335
Dot 5 is 400

When you run it again also change the range increments to 5 yards and it will be a lot more accurate. I was just aproximating based on the given info.