Some help figuring drop

Discussion in 'Long Range Hunting & Shooting' started by WMDM, Sep 22, 2018.

  1. WMDM

    WMDM Active Member

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    I searched for some time last night and can't wrap my head around it. Leupold doesn't have a ballistics calculator that I could find. Hopefully someone with more knowledge will help.

    Im trying to figure at what range I would use the lower point of the duplex reticle (point where the lower portion of the vertical cross hair transitions thinner) this would be at max (14) power. I will verify at the range soon but I was curious what the range would be.

    For anyone willing to try help here is the set up: 22" 243 Winchester, Hornaday Superformance 95 gr SST factory ammo, Leupold VX-3i 4.5-14x40 duplex. According to listed subtensions the "thin opening" is 5.4 at 14 power.

    I think that is all the info someone smarter than me should need LOL Thanks in advance for any help
     
  2. Hand Skills

    Hand Skills Well-Known Member

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    Without your zero and a measured velocity it's hard to say.

    With a 200yd zero you should be a couple of inches high using the post at 400. Test it out and let us know!
     
  3. WMDM

    WMDM Active Member

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    Oh yeah 200 yard zero! I have a similar set up I have run through my chrono. I'm betting I will be real close to 3,000 fps. Hornaday says velocity is 3185 but that's with 2" more barrel.
     
  4. Hand Skills

    Hand Skills Well-Known Member

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    Indeed, it's tricky to predict velocity. That being said, I'm confident you'll be on paper at 400. ;)
     
  5. woodnut

    woodnut Well-Known Member

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    Easy to do. Set zero at 100 yds. Not an inch high, dead on. Get a good, clear target for 300 yds. that you can see a small aiming point. Fire 3 rounds. You should be able to see the holes with your scope, but if not , view through a spotting scope. When you see the holes, find center of group and where it is located on your verticle crosswires. I'm betting it's at the point where the thick post tapers down to the fine wire. If it's lower, that could be small a problem. Higher, just do a "brain freeze" of that picture. Actually, the same way if it's lower. Hope this helps! Also, there are several ballistics apps in the Google store. I use Shooter.
     
  6. Rich Coyle

    Rich Coyle Well-Known Member

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    On my drop chart I have various power magnification corresponding with minutes of angle from the Crosshair to the top of that bottom post.
     
  7. Dog Rocket

    Dog Rocket Well-Known Member

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    5.4 what....inches or MOA?

    You can verify this yourself by shooting a group at 100 yards (no need to even change your zero) using the center crosshair, then shoot another group using the bottom post as an aiming point. The difference between them will be the subtention. Measure that distance center to center and divide by 1.047 to derive the number of minutes of angle.

    Use JBM or any other free ballistics calculator online and plug in your actual zero, speed, BC etc...Where the drop chart matches the subtention of the reticle, THAT is the zero for that point.
     
    Last edited: Sep 24, 2018
  8. lancetkenyon

    lancetkenyon Well-Known Member

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    I think the duplex reticle is 2MOA from center to top taper on the post @ 14x. So if you zero @ whatever (100, 200, etc.), top.of.post is 2 MOA lower.
     
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  9. Hatrick

    Hatrick Well-Known Member

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    Take a sighting in target at 100yds put the point on centerand read the horizontal line where the crosshair is.
     
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  10. dfanonymous

    dfanonymous Well-Known Member

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    You should record atmosphere when zero is set. The only reason we collect atmospherics in long range shooting is to have information that we know will effect the bullets flight. Since temp, elevation and pressure changes the density of air, recording what your zero was as will give a good baseline if you are writing dope cards as even for some ballistic calculators. Easiest to record drop on a pad and paper from 2 to whatever your max will be then just bring the data home and intepolate it into half then quarters. Easier said then done but that’s what works. If you are compelled to use a ballistic solver of sorts then take your data and interpolated data and true it to your real drop.
     
  11. Timnterra

    Timnterra Well-Known Member

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    I believe those numbers on the scope are supposed to correspond to a rangefinder of sorts. The 5.4 at 14x is supposed to be 540yds when a deer brisket to shoulder fits between the center crosshairs and the thick part of the bottom post. Leupold used to make a scope with a thin section in the reticle for this purpose but they now use the duplex itself. What this means is that at 14 power the distance between the center crosshairs and bottom post is roughly 16” at 540yds which is equal to roughly 3.2MOA. At 300yds 3.2 moa is about 9.6” which should be close to the drop of your 243 when zeroed at 100.
     
  12. WMDM

    WMDM Active Member

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    Thanks everyone for the info, I'm still trying to process it!