Magnification Effects on BDC Hash Marks
I had an interesting conversation with a fella today on the range. He noticed that I had a Burris Fullfield II mounted on my rifle and he asked me how I liked the BDC recticle. He said that he had the same scope and he found that the BDC was most effective on 9x power because the point of aim of the hash marks changed as he increased and decreased magnification.
To show me what he meant he had me put the crosshair on the parallel target bar at 3x magnification and then turn it up to 14x magnification. The crosshair didn't change position however the hash marks moved up the target changing the point of aim for them. I tried it with my Zeiss Conquest and it was the same thing. I've had good success using the hash marks out to 500 yards with my 30.06 and the Burris scope but I've always had it on 14x magnification. I haven't tried the Zeiss yet. The ballistic charts show +/- for the hash marks for different calibers and bullets but I don't recall ever seeing anything about magnification being factored in anywhere. I have to do some research on this but in the mean time........Does anyone know offhand if there is a desired magnification, whether maximum, minimum or somewhere in between, that a BDC recticle is the most accurate? |
If the secondary reticles are on the second focal plane their sub tension will change with magnification. That's how you adjust the Rapid Z for your particular load....you adjust the magnification according to the Zeiss calculator. This might help you understand a bit better
https://www.youtube.com/watch?v=uRmn...eature=g-all-u |
If you choose your reticle correctly for the trajectory of your load, the reticle will calibrate at close to the maximum magnification of the scope.
If you choose a reticle designed for a cartridge with a flatter trajectory than your load produces, you will need to turn the magnification down to calibrate the reticle. Let's say you go with a Rapid Z800 reticle for a 308win, if the scope is a 4.5-14, it could likely calibrate in the 8x-10x range. If you choose a reticle designed for a load with a much less flat trajectory, than your load ,you can't properly calibrate it. You can play with the point of impact at 200 yards to try and compensate, but it just won't as well as it is designed to do. An example would be using an RZ600 on a 22-250. |
I think Vortex makes a scope where the BDC moves with the magnification to help eliminate the change in impact.
So the BDC marks maintain the relative location as the magnification changes up and down. I am not sure how well it works though. LC |
My buckmaster bdc says it has to be on 10x to be most effect with the hash marks. However with there spot on ballistics calculator, you can print off a sheet that tells you when you're zerod at a certain range, what each hash mark represents.
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13.22 power?
Makes my 6X36 with the LR reticle seem like a revolutionary breakthrough in advanced simplicity. :) |
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Glad you enjoyed the video :) |
Thanks Sheephunter........great video. I though that you might respond to this thread. I'll have a look at the data page later on.:)
With your rifle, did you find that sighting in at 200 yards was more beneficial than sighting in at 100 yds because of what the data said? I wonder if the data for the Zeiss would work with my Burris scope as well. The magnification wouldn't change and I'm thinking that the hash marks should be the same??? |
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The Zeiss data will not work for the Burris as the sub tension of the secondary reticles would be different. Zeiss has a pretty tight patent on their system. |
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Agreed Chuck. Relatively simple! If you are running it out past 500 then I agree the Zeiss is the better system, or dial up. |
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400 yards really isn't that far any more though with the right gear. I can see the nostalgia of holding on to old technology but truthfully, the new stuff works better. You can't get better than knowing that each yardage indicated reticle is indeed zeroed for that yardage. You can get worse though. Why use something that may be good enough when there is a precise option? |
Contact your scope Manufacturer. They should be able to provide you with a rough chart indicating the change in minutes (or whatever unit you prefer) depending on what magnification you've got it set at.
Example: The Sightron SIII 6-24x50 - at min power, one hash mark interval represents 8 MOA, at max power, one hash mark interval represents 2 MOA...just an example. Most mfrs will give you that information at the very least and if you are lucky enough to have purchased a scope that is true to MOA, then you can do the math and make yourself a little chart listing the differences at different mag levels. But as TJ mentions, if consideration is given to this, one must weigh the advantages of 1st fp vs 2nd fp...depends on what you use it for.... |
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If the subtension of the 400 yard dot is for 20 inches of elevation and your 7mm is about 17 inches of drop and the 30-06 is 23, would you hit the plate? Better yet if I aim center mass would i kill the deer elk or whatever? If I am stillhunting through the trees and i have my Zeiss scope dialed down to 6X and I come out in the open, spot a deer at 400 yards, put that crosshair on him would I hit him. Oops forgot to turn the power ring up to 12.25X before I pulled the trigger........ For the record I have both Leupold LR's and Rapid Z's in my arsenal. I zero the LR 400 yard dot for whatever rifle i have it on and the 200 yard crosshair might be 219 and the 300 yard dot might be 305 and the 500 yard might be 521 but who cares, deer at those ranges will be dead. Unfortunately i am not sponsored by Zeiss. |
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The rest of your comments indicate you haven't even looked at that reticle. |
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Dont get TJ started on scopes!! rapid z is best out there.. :rolleye2:
Been there done that...lol |
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with most scopes its at max magnification for bdc but its still just a refrance and you have to shoot it to know it. every round has a diff muzzle vol. and diff weight bullets. will never be accurate for every gun..
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For this year I'll zero for 200 yds and restrict my hunting shots to a max distance of 300 yds, which I don't need a bdc for. Not a big deal as 95% of all the animals that I have ever shot were 200 yds or less and I've never shot one past 300 yds. Next year I'll practice until I'm confident with my shooting out to 500 yds. I can't afford to shoot several rds at each magnification from 200, 300, 400, 500 and 600 yds just to see what the optimum magnification is. I think that it would be better to understand the bdc recticle prior to practicing long range shooting so all that I have to do is confirm what the experts tell me (ie. the Zeiss data). Quote:
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Have the same scope
I have the same scope or did anyways on my 7mag. It is set up for max zoom to match the BDC. If you google search you will find the manual with common calibers and bullet selections. U can do the math to figure out ball park what each magnification will do to the point of impact. At 7x you have(theoretically) doubled your field of view which doubles your amount of usable drop in inches. This does not double the range u can shoot because we all know of the decaying arc that is the bullets trajectory. If u want I'm bored right now and if you send me your info on the bullet your shooting and I will match it up for u.:test:
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Assuming of course that game animals have now evolved to the same retardation level of their 2 legged persuers and stick around for charts, instruction manuals, smart phone apps, digital range finders with drop compensation, ballistic calculators, gps locators, athmospheric and windage kestrel meters, only to be killed by a newly developed mono metal bullet that penetrates deeper, leaves a glow in the dark blood trail, no lead contamination bullet......all within the comfort of a mossyoak seat cover. :)
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i will say the rapid z dose have a good bdc program very similer to the nikkon spot on program. as for glass the rapid z will beat the nikkon of cource..
almost forgot!! "Throws peanut" :scared0018: |
Dave. Try "Strelok" ballistic app for your Burris. It really is a good app. You can even use it to confirm what Zeiss says on the Zeiss website for your rapid z. The zeiss website will ask you if you want to optomize the reticle. If you select this it will tell you what magnification is the optimum in order to maintain the parameters of the hash marks.........200/300/400/500/600.
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