Dope vs ballistic calc

Raptor77

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I am relatively new to long range. Yesterday I went to the 1000 yard/mile range for the forth time in the last few months and am noticing a trend that I can't figure out. Multiple ballistic calculators give the same data. Load is chronographed per temperature, single digit SD. Data seems good out to 6-700 yards. At 1000 I have to at .5 to .75 MOA elevation and hold .5 left with no wind. At one mile I'm adding about 6 MOA elevation and almost 4 MOA left again with no wind. Shooting direction is East. Is the added elevation due to BC lowering with loss of speed? Is drift due to spindrift or rotation of Earth. Any help is appreciated.
 

Huskydriver

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You need to true your mv to the curve your using...

What ballistic calc are you using? How did you get your mv?
 

JustSendit

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I am relatively new to long range. Yesterday I went to the 1000 yard/mile range for the forth time in the last few months and am noticing a trend that I can't figure out. Multiple ballistic calculators give the same data. Load is chronographed per temperature, single digit SD. Data seems good out to 6-700 yards. At 1000 I have to at .5 to .75 MOA elevation and hold .5 left with no wind. At one mile I'm adding about 6 MOA elevation and almost 4 MOA left again with no wind. Shooting direction is East. Is the added elevation due to BC lowering with loss of speed? Is drift due to spindrift or rotation of Earth. Any help is appreciated.
Spin drift and Coriolis effect will both effect point of impact shifts at distances, specifically over 1000yds, compounded that is likely your horizontal shift, and could add to your elevation error as well.

You will need ensure your ballistic solver has the appropriate data, latitude, direction of fire and spin drift for your barrel twist rate. Ensure winds are accounted for as well, higher winds will effect the drop of the bullet.

Next, when bullets enter transonic the prediction of their flight path is often not in line with what ballistic solvers give to the shooter. Check out a few sources for calibrating solvers into distances beyond transonic. For instance AB solvers will true +/-10% into transonic then utilizing the Drop Scale Factor (DSF), make adjustments to the ballistic curve based on your data you input - for further distances. I.e true at 800yds, DSF at 1000yds then 1200yds ect ect. The DSF adjusts the ballistic curve based on those inputs.
 

Raptor77

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You need to true your mv to the curve your using...

What ballistic calc are you using? How did you get your mv?
Got MV from my Caldwell shronograph. Used several ballistic calcs including JBM ballistics, bullet drop app and Hornady 4dof.
 

Steel head

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Since your good to 600ish and out after that a BC adjustment is probably in order.
What bullet are you shooting?
Out to a mile a lot of combinations need a multi BC curve or DSF.
 
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Matches Malone

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I am relatively new to long range. Yesterday I went to the 1000 yard/mile range for the forth time in the last few months and am noticing a trend that I can't figure out. Multiple ballistic calculators give the same data. Load is chronographed per temperature, single digit SD. Data seems good out to 6-700 yards. At 1000 I have to at .5 to .75 MOA elevation and hold .5 left with no wind. At one mile I'm adding about 6 MOA elevation and almost 4 MOA left again with no wind. Shooting direction is East. Is the added elevation due to BC lowering with loss of speed? Is drift due to spindrift or rotation of Earth. Any help is appreciated.
If you’re NOT using a custom curve and using a g1 or g7 BC then yes, you will have to change your Bc to match exact dope at different distance. Hornady has a pretty good example of different g7 scales per velocity range (mach) and how it effects their specific bullets.
 
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Seymour Fish

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I am relatively new to long range. Yesterday I went to the 1000 yard/mile range for the forth time in the last few months and am noticing a trend that I can't figure out. Multiple ballistic calculators give the same data. Load is chronographed per temperature, single digit SD. Data seems good out to 6-700 yards. At 1000 I have to at .5 to .75 MOA elevation and hold .5 left with no wind. At one mile I'm adding about 6 MOA elevation and almost 4 MOA left again with no wind. Shooting direction is East. Is the added elevation due to BC lowering with loss of speed? Is drift due to spindrift or rotation of Earth. Any help is appreciated.
Shooting due East, the apparent Rise in the target during the hang time to 1K is 2.6”/sec, thus you will hit low. Coriolis. Spin drift at same will be 0.6-1 MOA range roughly. Wind from your left will give aerodynamic jump which might amount to 0.25 MOA Low impact in addition to the above. N hemisphere, Rt hand twist.
 
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jasent

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Every thing has been covered except that fact that there is NEVER no wind. Especially when shooting at one mile when your bullet travels way above line of site. Second have you done a tall target test and measured your scopes “click” value? Never assume it’s right, verify
 

Raptor77

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Since your good to 600ish and out after that a BC adjustment is probably in order.
What bullet are you shooting?
Out to a mile a lot of combinations need a multi BC curve or DSF.
300 Win Mag 225g Hornady ELD Match over 66.3g H4350 seated .003 from the lands.
 

Bandit320

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Got MV from my Caldwell shronograph. Used several ballistic calcs including JBM ballistics, bullet drop app and Hornady 4dof.
Have you tried the AB Mobile app (what it is called on the iPhone)? They offer custom drag models which claim to be developed from live fire testing. This is a link were they talk about it.


I have used their CDM for the 225 ELDM and it seems to predict trajectory well.

Mike
 

johnbrody0317

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Not sure what caliber you're running but you might be going trans sonic far before. If so try finding that range and truing.
 

Sloblk8

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I'm actually going through the same issues. Today at 1800 yards the calculator said 21.9 mils and ended up being closer to 25. At 1100 its about a mil off. I tried to trueing it in the past but when I did everything seemed to be off so I put it back and just started to keep track of how much to add to what the calculator says. I would like to know why as well. I know I need a better ballistic calculator as I'm using streloc pro but I may mess around with trueing again and see what happens.
 

jasent

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I'm actually going through the same issues. Today at 1800 yards the calculator said 21.9 mils and ended up being closer to 25. At 1100 its about a mil off. I tried to trueing it in the past but when I did everything seemed to be off so I put it back and just started to keep track of how much to add to what the calculator says. I would like to know why as well. I know I need a better ballistic calculator as I'm using streloc pro but I may mess around with trueing again and see what happens.
Tall target test is in order. Very simple to do. Get a target as tall as you can. Must be exactly 100 yards. Put your poa at the bottom. Shoot it. Dial 30 or 40 moa. Shoot again. Dial back to zero. Shoot dial back up and shoot. Once you have 2 5 shot groups measure center to center of each group. Then do the math. Moa dialed x 1.047” if your tacking true you’ll know. If not figure the difference and make the appropriate adjustments in your solver and don’t worry about it. FYI my cheapest scope is the most true I have, most are about 2% one is 4% off. No big deal once you know how to fix the issue
 

Steel head

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I'm actually going through the same issues. Today at 1800 yards the calculator said 21.9 mils and ended up being closer to 25. At 1100 its about a mil off. I tried to trueing it in the past but when I did everything seemed to be off so I put it back and just started to keep track of how much to add to what the calculator says. I would like to know why as well. I know I need a better ballistic calculator as I'm using streloc pro but I may mess around with trueing again and see what happens.
3 mils is pretty big divergence
Tall test is in order
How are you getting your environment data?
Possibly a head wind?
 

Sloblk8

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Tall target test is in order. Very simple to do. Get a target as tall as you can. Must be exactly 100 yards. Put your poa at the bottom. Shoot it. Dial 30 or 40 moa. Shoot again. Dial back to zero. Shoot dial back up and shoot. Once you have 2 5 shot groups measure center to center of each group. Then do the math. Moa dialed x 1.047” if your tacking true you’ll know. If not figure the difference and make the appropriate adjustments in your solver and don’t worry about it. FYI my cheapest scope is the most true I have, most are about 2% one is 4% off. No big deal once you know how to fix the issue
I'll give that a shot next time I go out, hadn't seen that before. I never worried too much because it was fairly predictable so I just delt with it. I figured the bullet was slowing more than the solver was predicting. Thanks for the help.
 

Sloblk8

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3 mils is pretty big divergence
Tall test is in order
How are you getting your environment data?
Possibly a head wind?
I'm using my smart watch for barometric pressure and a digital thermometer. Then just looking on my phone for humidity. I need a Kestrel lol. As far as wind it seems its pretty solidly blowing left but there definitely could be a little bit of a headwind.
 

Steel head

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I'm using my smart watch for barometric pressure and a digital thermometer. Then just looking on my phone for humidity. I need a Kestrel lol. As far as wind it seems its pretty solidly blowing left but there definitely could be a little bit of a headwind.
What bullet and speed?
 

Steel head

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6.5 creedmoor, I don't reload yet so of the shelf Hornady 147 eld match. Speed average was 2720.
I had to use a substantially lower BC for the 147’s for my mile and further shots.

In fact you’re actual come up was not really far from my actuals, I had them going a bit over 2800.

A BC change will probably get you app in line.
I think I used a .325-.330 G7.
 

Sloblk8

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I had to use a substantially lower BC for the 147’s for my mile and further shots.

In fact you’re actual come up was not really far from my actuals, I had them going a bit over 2800.

A BC change will probably get you app in line.
I think I used a .325-.330 G7.
Awesome, I'll definitely play with that. I have 0.697 G1 in currently, which is what Hornady says the BC is. I know that usually isn't correct but I thought it was close because it seems to be on target or very close up to 1100-1200. I'll make a duplicate gun slot to play around with the BC. What would the G7 equivilant be close to do you think? Thanks.
 
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