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Old April 21, 2013, 01:46 PM   #1
ndking1126
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Using Ballistic Software to Determine Ballistic Reticle Zero

I haven't been able to figure out the math on this but it seems to me it should be possible. I've got a scope with the Ballistic Plex reticle on my .30-06 and I'd like to find out the (theoretical) zero of each hash mark.

If I put the scope on full zoom and find out how many inches exist between each mark at 100 yards (ex: 200 yard line is 2" below the 100 yard, 300 yard line is 6.5" below, 400 line is 12"), it seems to me I should be able to go into something like JBMBallistics.com and figure out where each one is zereod at, based on my elevation, exact bullet BC and muzzle velocity. How would I go about doing that?

I know the most important thing is to go out and actually shoot at those distances to verify, but I think this would be a really good way to figure out what to expect. I used to be good at this kind of stuff in high school and college.. it's just been along time!
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Old April 21, 2013, 01:58 PM   #2
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You're on the right track. Most scope manufacturers post their reticle subtensions, and the others should tell you what they are if you ask. Bullet manufacturers publish their BC's, but some of them exaggerate.
What scope and bullet are you using, and have you chronographed your load?
Scope height above bore makes some difference, also.
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Old April 21, 2013, 02:02 PM   #3
ndking1126
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I've got the Burris Ballistic Plex and I'm currently loading up 165gr Ballistic Tips shooting it out of a .30-06. It's a Fullfield II 4.5-14x42. I don't have a chronographed speed yet, as I'm new to reloading and am currently just making sure I don't permanently alter my face and can come up with a good recipe my rifle likes.

I looked on their website and couldn't find this measurement, just the thickness of the reticle lines. My plan was too draw a ruler on my target post, put it out at 100 yards and just see where the lines fall. Not extremely high tech, but it should work. I just send them an e-mail asking if they had it, hopefully I'll hear back.

Any mathematicians or ballisticians out there that can help?
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Old April 21, 2013, 02:18 PM   #4
603Country
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In the box with the Burris FFII scope, they include some very useful data on the Ballistic Plex lines. I don't have it in front of me, but they included BDC data for many calibers and for several bullets and velocities in those calibers. You can also google up the data. Personally, I found the Burris data much easier to quickly understand than what came with my Leupold VX-2 in 6-18 to explain their BDC lines.

So I just now went to Google and had a look at the data. They show the 30-06 and the 165 gr bullet, with a mv of 2800. Sighted in at 100, the Plex lines show a drop at 200 of 3.1 inches versus anticipated actual drop of 4 inches. For 300, the plex line allows for a 13.5 inch drop, vs anticipate actual of 14. For 400 yards, it's 30.1 for plex vs an actual of 32 inches drop. For 500, plex allows fir 55.3 inches drop, where actual should be more line 59. Note that this is Burris data and I have not checked anticipated actual drops in my ballistic program on the iPad.

I've got a couple of the 4.5-14 Burris FFII scopes and I like them and have used those lines quite a few times on long coyote and pig shots (about 400 yards). I have to admit that it took some effort for me to trust the lines, since I hadn't actually tested the bullet drop out to 300 or 400 yards. But I just decided that I'd eventually have to do it, and here was a good opportunity. I cranked the magnification to 14 and squeezed the trigger and the coyote (and later the pig) dropped like a rock when the 120 gr from my 260 hit him.

Last edited by 603Country; April 21, 2013 at 02:45 PM.
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Old April 21, 2013, 02:59 PM   #5
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With the info on the Burris site, and the online ballistic calculators, it never occurred to me to try to do the math myself.
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Old April 21, 2013, 07:22 PM   #6
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I've found that the scopes with some type of long range recicles to be pretty close. I just zero at 100 yards with the crosshairs. The 200, 300, and 400 yard dots are so close it just doesn't matter. EVen when using different bullet weights and speeds. There is far less difference in bullet drop than most guys realize. At 400 yards my 180 gr 30-06 loads drop 1" more than my 165's and 2" more than my 150's.

I just went out and started shooting. At longer ranges My 150 gr loads group right at the top edge of the dot, 165's right in the middle and 180's just on the bottom edge of the dot.

Even after you spend all the time doing the math, you're still gonna have to shoot to be sure anyway. Rather than giving myself a headache with the math I just went to the range and started shooting.

The only time it might make any real difference is if you have a rifle capable of 1" groups at 400 yards. Then you need to have exact drop data.
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Old April 21, 2013, 08:22 PM   #7
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If you have a smart phone or tablet computer, download the app from Strelok. Its a ballistic calculator with options for scope reticles from many manufacturers. Burris ballistic plex is one of them.

If you don't have a tablet or smart phone just shoot it. The ballistic plex is designed to match the 30-06 trajectory. As was already mentioned most cartridges are fairly close.
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Old April 21, 2013, 09:30 PM   #8
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Quote:
download the app from Strelok. Its a ballistic calculator with options for scope reticles from many manufacturers
I did this for my vortex . I have not used it at the range or in the field but it has many reticles to chose from and you can save the data for 10 different rifles or loads . Very cool . I have the app on my iphone it's called iStreloc and for my reticle there is is a magnification slide bar . As you increase or decrease the mag the yardage on the corresponding hash marks change .
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Old April 22, 2013, 07:20 PM   #9
603Country
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I had been using iSnipe on the iPad, but just switched to iStrelok. Very nice and I REALLY like being able to pull up all sorts of BDC data for Burris and Leupold. Thanks for the suggestion.
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Old April 22, 2013, 09:13 PM   #10
ndking1126
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Big al hunter, Ive had Strelock on my phone basically since I bought it but never noticed that it would put the distances on each line of the reticle, exactly like I'm trying to do.. thanks for recommending I go back into it. I liked the program already, but this makes it that much better! Amazing program for being free.

The nerdy side of me would still like to know how to calculate it, lol. I'm pretty sure ill just stick to strelock though. Thanks everyone for your feedback!
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Old April 23, 2013, 12:29 AM   #11
big al hunter
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Quote:
The nerdy side of me would still like to know how to calculate it, lol.
Ok lets use your example.

Quote:
: 200 yard line is 2" below the 100 yard, 300 yard line is 6.5" below, 400 line is 12"
Assuming that this is looking at the reticle through your scope at 100 yards, and that you have a ruler hanging next to your target.

At 200 yards the reticle will subtend 2x as much as at 100 so the first line under the crosshair is 4 inches lower, the 2nd line is 13 inches lower, the 3rd line is 24 inches lower than the crosshair.

At 300 yards it subtends 3 times as much as at 100 so the first line is 6 inches below the crosshair, the second line is 19 1/2 inches below, the 3rd line is 36 inches below.

You can continue on using the hundreds of yards divided by 100 as your multiplier. Such as 225 yards distance to target, multiply the measurement at 100 yards by 2.25. Or x 5 if your distance to target is 500 yards.

Since your scope probably lists the reticle subtension in MOA you have to convert it. 1'MOA is about 1.05 inches at 100 yards. So if the scope manufacturer says the first line below the crosshair subtends 3 MOA multiply 3 x 1.05 = 3.15 inches at 100 yards.

If your gun can shoot accurately enough to need the .05 for calculations use it, if not the math is easier to use 1 inch as 1 MOA at 100 yards, 2 inches is 1 MOA at 200 yards and so on.
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