So my buddy has a 243 AI. He is shooting 105 Berger vlds at 3200, zeroed at 100. Twist 1/8. He’s using an Athlon Helos BTR First focal plane. The issue he is having is that when he inputs all this data into any ballistic calculator, his firing solutions are just wrong. We know his velocity is correct, we’ve verified it with a Labradar and magnetospeed. For example, Ballistic AE calculates his 500 yard solution to be 7.15 MOA. However, he was consistently shooting over when he dialed to 7. He figured out he needed to dial to 6.25. Our first thought was the scope is not tracking correctly. However, he also had to hold 6.25 in the reticle to get accurate center hits. It gets worse and worse the farther he shoots. Ballistic AE has him shooting 1.5 to 2 MOA high at 900 yards. We can’t figure out what we are missing here. Are we expecting too much from ballistic calculators? Any suggestions?
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Ballistic Calculator Wrong
- Thread starter Kbroad
- Start date
Inside 1000 is hard to believe the calculator is wrong, unless the inputs are wrong. You know, garbage-in, garbage-out. At that distance, your cartridge is supersonic and even the worst app shouldn't give you that much leery.
My thoughts exactly. It’s worked fine with every other load I have ever put in. I can’t figure out what I’m missing though.
105 VLD G7 0.272
3200 fps
440 altitude
50 degrees
Zeroed at 100
105 VLD G7 0.272
3200 fps
440 altitude
50 degrees
Zeroed at 100
The other thing I forgot to mention is that the targets are at known distances so that’s another variable that can be eliminated
Verify that your settings are all correct. As stated above, garbage in garbage out. Are you using Station Pressure or Barometric Pressure? Sight height above bore, G1 vs G7, etc... All these things alone won’t equate to a miss, but combined, it’s possible.
Check your settings. See if there is something in the "zero offset" or maybe the "LOS Angle" or "Cant Angle" fields. Certainly sounds like a data entry error somewhere.
At 500 yards your 0.9moa miss is approximately 5 inches high. At 900 yards, your misses are 1.5 to 2.0 moa, roughly double what they are at 500yds, suggesting a linear progression, which itself suggests an input problem.
Just a few possibilities / thoughts:
Applied Ballistics suggests that when there's an impact variance within supersonic range, the first factor to be checked is muzzle velocity. The only way that I could see your m.v. values might be at fault here is through effects of temperature on your ammo.
1) ammunition / ambient temperature: is it possible that your muzzle velocity was recorded at a lower temperature? if you record a muzzle velocity at low ammo temps, on a warm day you will shoot over what your colder-ammo m.v. might lead you to believe. i'm not familiar with too many calculators, as I calculate ammo/temp curves by hand before going to the range, but is it possible the values you entered into your calculator didn't account for temperature variations? Both ammo and ambient can make a big difference, and would be the first place to double check. For example, if you recorded 2850 at 60*F ambient, and 60*F ammo, then shot at 90*F ambient, and 110*F ammo (from sitting in the sunlight, for example) and didn't correct for it, you gonna go sailing way over. A warmed-up chamber is another possibility. The slope of the velocity curve increases as ammo temperature increases, so a small increase in temp can make a bigger-than-expected difference in m.v.
Assuming that your MV is properly recorded and temperature-adjusted, there are a couple realistic possibilities given the list of environmentals you posted:
2) atmospheric pressure: I noticed in your list of environmental data you listed an altitude. If your program uses a generic barometric pressure (an assumed pressure for a given altitude without regard for the real, actual, measured pressure), this would more than account for the differences you noticed. On ballistics tables that are corrected for pressure, at increasing distances a 1.0 in Hg can make a surprising difference in elevation. A lower pressure than the solver uses can change the trajectory, even with consistent m.v.
3) any crosswind-induced aerodynamic jump and D.o.F. dependent vertical coriolis might be adding some variance to this vertical dispersion, although without knowing more details about your shooting latitude and wind dynamics, it's impossible to say whether it will add that much. The math says that it is conceivable that those two could combine to account for a miss like that, assuming everything else is correct. I'm dubious on this, though, because that would require a unique set of circumstances.
4) tailwind can make you impact high when everything else is corrected for. Crosswind correction tables usually have a horizontal correction, but rarely include vertical corrections. A wind that is "no-value" for horizontal correction is definitely a "value" for vertical correction.
Varying m.v., wind direction, wind speed, latitude, direction of fire, incorrect station pressure are all possibilities that could aid this miss.
The "garbage in - garbage out" as noted above can lead people to lose faith in their ballistic solvers when the solvers are only computing with what they're given. Projectile ballistics is fairly straightforward, so the odds suggest a breakdown in the data input somewhere.
Holy Smokes, sorry for the essay, lol, just some possibilities to consider...
Just a few possibilities / thoughts:
Applied Ballistics suggests that when there's an impact variance within supersonic range, the first factor to be checked is muzzle velocity. The only way that I could see your m.v. values might be at fault here is through effects of temperature on your ammo.
1) ammunition / ambient temperature: is it possible that your muzzle velocity was recorded at a lower temperature? if you record a muzzle velocity at low ammo temps, on a warm day you will shoot over what your colder-ammo m.v. might lead you to believe. i'm not familiar with too many calculators, as I calculate ammo/temp curves by hand before going to the range, but is it possible the values you entered into your calculator didn't account for temperature variations? Both ammo and ambient can make a big difference, and would be the first place to double check. For example, if you recorded 2850 at 60*F ambient, and 60*F ammo, then shot at 90*F ambient, and 110*F ammo (from sitting in the sunlight, for example) and didn't correct for it, you gonna go sailing way over. A warmed-up chamber is another possibility. The slope of the velocity curve increases as ammo temperature increases, so a small increase in temp can make a bigger-than-expected difference in m.v.
Assuming that your MV is properly recorded and temperature-adjusted, there are a couple realistic possibilities given the list of environmentals you posted:
2) atmospheric pressure: I noticed in your list of environmental data you listed an altitude. If your program uses a generic barometric pressure (an assumed pressure for a given altitude without regard for the real, actual, measured pressure), this would more than account for the differences you noticed. On ballistics tables that are corrected for pressure, at increasing distances a 1.0 in Hg can make a surprising difference in elevation. A lower pressure than the solver uses can change the trajectory, even with consistent m.v.
3) any crosswind-induced aerodynamic jump and D.o.F. dependent vertical coriolis might be adding some variance to this vertical dispersion, although without knowing more details about your shooting latitude and wind dynamics, it's impossible to say whether it will add that much. The math says that it is conceivable that those two could combine to account for a miss like that, assuming everything else is correct. I'm dubious on this, though, because that would require a unique set of circumstances.
4) tailwind can make you impact high when everything else is corrected for. Crosswind correction tables usually have a horizontal correction, but rarely include vertical corrections. A wind that is "no-value" for horizontal correction is definitely a "value" for vertical correction.
Varying m.v., wind direction, wind speed, latitude, direction of fire, incorrect station pressure are all possibilities that could aid this miss.
The "garbage in - garbage out" as noted above can lead people to lose faith in their ballistic solvers when the solvers are only computing with what they're given. Projectile ballistics is fairly straightforward, so the odds suggest a breakdown in the data input somewhere.
Holy Smokes, sorry for the essay, lol, just some possibilities to consider...
A little more information for context. We have the Labradar set up every time we shoot so we know actual velocity for that temperature when we do the calculations. While we are out shooting, we are calculating for 3 or 4 rifles other than this 243 AI and it is giving correct come ups. I didn’t realize it but his son is shooting these same 105 VLDs in a 6mm creedmoor and is having the same issue with incorrect calculations. Makes me think maybe the BC is wrong in the app? Just a thought. I’m showing .272 G7.
You have to TRUE the software, the computer only knows this stuff in a vacuum, you and your equipment is the variation
1. Calibrate your Scope and tall target test it - Scope errors are the number cause of bad data. Most optics in your price range are 2% off, plus if your scopes is IPHY vs MOA that is a big error factor.
2. True the Data by adjusting the BC based on your 800-yard drop. So you have to change the BC to match your system. Barrels, Powder, MV, etc all have an affect on the BC number.
3. Fine tune the closer ranges using the MV. Adjust it up or down, if you have to go over 50fps at this point there is probably another issue, but some people have to adjust their MV over 100fps for 3DOF solvers.
1. Calibrate your Scope and tall target test it - Scope errors are the number cause of bad data. Most optics in your price range are 2% off, plus if your scopes is IPHY vs MOA that is a big error factor.
2. True the Data by adjusting the BC based on your 800-yard drop. So you have to change the BC to match your system. Barrels, Powder, MV, etc all have an affect on the BC number.
3. Fine tune the closer ranges using the MV. Adjust it up or down, if you have to go over 50fps at this point there is probably another issue, but some people have to adjust their MV over 100fps for 3DOF solvers.
This is a good post to get most of the way down the road toward converging your calculator to reality.
Just had same issue. Phone was inputting shooting angle from camera. Turned feature off and all is well.
Using Berger information the Target 105 VLD BC is .265. The Hunting 105 VLD is .278 - both G7. Using your information, scope height of 2.0" and the Hunting VLD the 500 yard solution is under 7 MOA (6.73 MOA). http://bergerbullets.com/ballistics/php/bb.php
Had this same issue a couple weeks ago the "get" button got pressed some how and all the data was off
Doesn't Ballistic AE have a bullet library? Did he Zero off a bench and was shooting prone? Was it consistently hitting the same amount high at all distances?
Also did you chrono the loads again/did he use a magneeto speed? if so did he zero with it on?
Also did you chrono the loads again/did he use a magneeto speed? if so did he zero with it on?
I use Applied Ballistics. I put in the right information and it gives me numbers that are just flat wrong. I shoot at a range with KD targets every 100 yards to 1k, I have checked the actual ranges with a good LRF. I have to adjust the MV and BC in order to get the numbers to match targets. I have checked scope tracking and repeatability - i'm good. I checked scope height using manufacturers drawings and double-checked with calipers. I checked the barrel twist. I adjust for temp and station pressure. I use an Oehler 35 for velocities - AB computes the wrong curve. Even with adjusted numbers, the predictions in the middle of the range don't match the predicted curves, they just don't look the same. Many people seem to get numbers from these solvers that they can shoot with, I could not use AB without good gun data. Perhaps the OP is having a similar issue.
Once I have adjusted the inputs to predict a curve that matches what I see when I shoot, I use the tool to create an "ups" chart with numbers every 25 yards until the bullets are solidly sub-sonic - roughly 900 yards with 308 175 SMK at 2615 or 2640 (depends on the gun and barrel length). I use the computed flight times for a mover chart.
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