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CO, USA
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Posted: 2/28/2019 2:17:12 AM EDT
I was using the online Hornady calculator to calculate bullet drop at various distances. For a given bullet at 200 yards I got 48". I was later playing with the Hornady Android app and putting in the same details I got 85". That's a huge difference for the same data. The app asks for barrel twist and playing around with it I found that setting it to 1:4 gave me the same data as the website but using 1:16 (actual twist for .357) gave me 85".
Is there really that much impact from twist? If so, why is the website calculator not asking for twist or otherwise using a standard for the caliber? I was the using the "standard" calculator in both examples not the newer 4DOF calculator. Other calculator like the one on gundata.org also give the same results as the hornady website. Given the hugely different values, any idea which calculator to trust? If the app using the barrel twist data then that would suggest most of the online calculators are wrong. |
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Posted: 2/28/2019 3:30:24 AM EDT
[#1]
The only online calculator I use is the JBM one...
http://www.jbmballistics.com/ballistics/calculators/calculators.shtml |
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Posted: 2/28/2019 3:30:33 AM EDT
[Last Edit: HighpowerRifleBrony]
[#2]
I forget the term, but I've heard that a bullet spun extra fast can remain pointed upwards (parallel-ish to the bore line) longer than it should, instead of nosing over to follow the parabola. I'm not sure by how many degrees, how far, and how much the trajectory would change.
Try a 55gr .224 from a 1:12, then a 1:4. Perhaps extend the range to 600-800yds. ETA: I use JBM as well. |
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Posted: 2/28/2019 7:25:08 AM EDT
[Last Edit: popnfresh]
[#3]
I suspect user error or a fucked up calculator that doesn't tolerate twists outside the norm.
Spin drift on. Wind and twist rate effecting drift. Twist rate does nothing to the drop at these distances  Attached File Attached File. . . Spin drift off. Wind is only effecting drift  Attached File Attached FileBTW My inputs were just guesses, no idea what your details are, " 357" is pretty vague . If you're shooting a pistol with a 25yd zero then the drop would be 40" at 200 with my guessed inputs, I just used a 100yd zero. |
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Posted: 2/28/2019 10:03:31 AM EDT
[#4]
Quote HistoryOriginally Posted By AKSnowRider:
The only online calculator I use is the JBM one... http://www.jbmballistics.com/ballistics/calculators/calculators.shtml |
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Posted: 2/28/2019 10:08:37 AM EDT
[#5]
Originally Posted By phdog:
I was using the online Hornady calculator to calculate bullet drop at various distances. For a given bullet at 200 yards I got 48". I was later playing with the Hornady Android app and putting in the same details I got 85". That's a huge difference for the same data. The app asks for barrel twist and playing around with it I found that setting it to 1:4 gave me the same data as the website but using 1:16 (actual twist for .357) gave me 85". Is there really that much impact from twist? If so, why is the website calculator not asking for twist or otherwise using a standard for the caliber? I was the using the "standard" calculator in both examples not the newer 4DOF calculator. Other calculator like the one on gundata.org also give the same results as the hornady website. Given the hugely different values, any idea which calculator to trust? If the app using the barrel twist data then that would suggest most of the online calculators are wrong. 
As mentioned spin drift will be added in and will effect. 4Dof adds in spin drift. |
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Posted: 2/28/2019 3:22:15 PM EDT
[#6]
Quote HistoryOriginally Posted By Rob01: If you use any ELDs you should try the 4Dof. It's more accurate than JBM especially at longer ranges. I have used JBM for years and I use the 4Dof now for everything but rimfire. |
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Posted: 2/28/2019 4:52:56 PM EDT
[#7]
The app is free and you can also play with it on the Hornady site.
But you should be running those 225 ELDs.
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Posted: 2/28/2019 6:27:53 PM EDT
[#8]
Quote HistoryOriginally Posted By Rob01:
The app is free and you can also play with it on the Hornady site. But you should be running those 225 ELDs.  Attached File |
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CO, USA
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Posted: 2/28/2019 6:40:31 PM EDT
[#9]
I'm willing to accept that I could have made a mistake, but I don't think so. Here are two screen captures of the exact same data with literally only barrel twist being different. First with 1:4 and second with 1:16. If barrel twist has no impact then the app is screwed up.
1:4 
1:16 (actual twist of Ruger Blackhawk) 
I'm trying to figure out how to share a PDF of the printout from the Hornady website. |
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CO, USA
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Posted: 2/28/2019 6:43:06 PM EDT
[#10]
Quote HistoryOriginally Posted By Rob01: First stop running data in inches. Now I need to know if drop at 200 yards is 85" or 48". Big difference. |
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CO, USA
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Posted: 2/28/2019 6:59:29 PM EDT
[#11]
Okay, made an image instead of the Horandy website output with all the inputs as well. As you can see, very similar to the app IF you use 1:4 twist. Otherwise, it's way off.
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Posted: 2/28/2019 7:21:23 PM EDT
[#12]
Quote HistoryOriginally Posted By phdog:
Why? MOA or Mil isn't useful to me with open sights on a revolver. Also, I'm trying to determine how sight picture needs to change for a 200 yard shot and the formula I'm using uses inches so inches are precisely what I need to know. Now I need to know if drop at 200 yards is 85" or 48". Big difference. What you should use is the twist that the pistol has in it to figure your data. Ballistic programs are garbage in, garbage out so if you use the wrong data you will get the wrong numbers. Who cares what 4 twist will do if your pistol has a 16 twist. Right? |
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CO, USA
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Posted: 2/28/2019 7:44:29 PM EDT
[Last Edit: phdog]
[#13]
Quote HistoryOriginally Posted By Rob01: Well seeing as it's the precision rifle section I assumed you were using a scope or sights with MOA. Quote HistoryOriginally Posted By Rob01: Well seeing as it's the precision rifle section I assumed you were using a scope or sights with MOA. What you should use is the twist that the pistol has in it to figure your data. Ballistic programs are garbage in, garbage out so if you use the wrong data you will get the wrong numbers. Who cares what 4 twist will do if your pistol has a 16 twist. Right? I don't think the app is total garbage though as the data for my .308 is real close to what the various website calculators show. ETA: oh, and I played around with the app some more. I get very similar output for all barrel twists up to 1:12 of approx 48". 1:13 changes to 52", 1:14 goes to 68", 1:15 is now 77" and 1:16 is 85" |
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Posted: 3/1/2019 12:38:21 AM EDT
[#14]
I looked at the 4DoF. It won't calculate a 73gr ELD through a twist faster than 1:7; saying it's outside of the min/max values of 4-20.
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Posted: 3/1/2019 7:46:46 AM EDT
[Last Edit: popnfresh]
[#15]
Quote HistoryOriginally Posted By phdog:
Fair enough. But I couldn't find a "precision revolver" section :) I agree that I should use the right twist, but what I'm confused by is the fact that all the online calculator including the JBM give output that is in line with the Hornady app only when using the wrong twist. So, either the Hornady app is garbage or all the website calculators are wrong. The website calculators might be using something like 1:8 or 1:10 as a default since that's close to what many precision rifles use but then that falls apart when using something like .357. I don't think the app is total garbage though as the data for my .308 is real close to what the various website calculators show. ETA: oh, and I played around with the app some more. I get very similar output for all barrel twists up to 1:12 of approx 48". 1:13 changes to 52", 1:14 goes to 68", 1:15 is now 77" and 1:16 is 85" Shitcan that app and get Shooter or Strelok or AB mobile. Give me your data, bullet, MV and zero distance.EDIT nevermind got it. By the way you cannot be at 6000 feet and have a pressure of 29.0 inHg I'll assume 6000feet and 24.0inHg since you're in CO. Edit for .158 bc Spin off zero wind  Attached File Attached FileSpin drift on zero wind  Attached File Attached File |
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Posted: 3/1/2019 8:42:41 AM EDT
[Last Edit: popnfresh]
[#16]
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Posted: 3/1/2019 9:14:13 AM EDT
[Last Edit: popnfresh]
[#17]
Shooter
 Attached File Attached FileJBM  Attached File Attached File4 out of 5 solvers agree, 47" of drop regardless of twist rate. End of discussion. 
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Posted: 3/1/2019 11:14:26 AM EDT
[Last Edit: popnfresh]
[#18]
A couple more I guess
AB Analytics  Attached File Attached File. I have no idea what's wrong with Hornadys solver.....but this is my first time using it (and last). Restarted my phone, tried the simple and 4dof " shrug". That is not a mistake, the 4 twist almost agrees with all the other solvers.  Attached File.  Attached File. |
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Posted: 3/1/2019 12:30:11 PM EDT
[#19]
Hornady does better on a slightly more normal setup.
 Attached File Attached File.  Attached File Attached File. |
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Posted: 3/1/2019 12:35:31 PM EDT
[#20]
4Dof works perfectly fine for what it was designed for. Used it all last year and it was right on when proper data was put in. Shot it in matches to over 1250 yards with multiple calibers.
Just because it doesn't work with a pistol caliber with a crazy fast twist that the pistol doesn't even have doesn't mean it's useless. With the proper info it seemed like it worked well. I still don't understand the reason to even run it with a 4 twist. |
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Posted: 3/1/2019 12:44:59 PM EDT
[Last Edit: popnfresh]
[#21]
Quote HistoryOriginally Posted By Rob01:
4Dof works perfectly fine for what it was designed for. Used it all last year and it was right on when proper data was put in. Shot it in matches to over 1250 yards with multiple calibers. Just because it doesn't work with a pistol caliber with a crazy fast twist that the pistol doesn't even have doesn't mean it's useless. With the proper info it seemed like it worked well. I still don't understand the reason to even run it with a 4 twist. JBM, Strelok, Shooter, AB Mobile and AB Analytics all agree with each other. |
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Posted: 3/1/2019 12:49:17 PM EDT
[#22]
No idea. Maybe he should call Hornady. I only use it in the app for the bullets in the drop down and it works fine for all the rifles and calibers I have used it. It's a free app and online so if he doesn't like it he isn't out anything but for rifles it works great.
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CO, USA
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Posted: 3/1/2019 2:13:24 PM EDT
[#23]
I sent a request to Hornady so we'll see what they say.
Thanks for all the data confirming that app is eff'd up with respect to .357 Quote HistoryOriginally Posted By Rob01:
No idea. Maybe he should call Hornady. I only use it in the app for the bullets in the drop down and it works fine for all the rifles and calibers I have used it. It's a free app and online so if he doesn't like it he isn't out anything but for rifles it works great. If I hear back from Hornady I'll post their feedback. |
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Posted: 3/1/2019 3:21:09 PM EDT
[#24]
Quote HistoryOriginally Posted By phdog:
I sent a request to Hornady so we'll see what they say. Thanks for all the data confirming that app is eff'd up with respect to .357 I'm curious. Is it a bug? Is using a 1:10 twist (less unrealistic and still give better output than 1:16) a reasonable work around (i.e. repeatable)? I don't know. Just exploring. If I hear back from Hornady I'll post their feedback. |
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CO, USA
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Posted: 3/1/2019 3:25:11 PM EDT
[Last Edit: phdog]
[#25]
Quote HistoryOriginally Posted By popnfresh:
Use Strelok or JBM for pistol I guess, they are free. ETA: I don't see a JBM app for Android. Strelok gives similar output but the interface is crappy. I like the Hornady interface better. Options are good though. For now, might just use the Hornady app and set the twist so that it gives correct output. I'll need to test some different distances though to make sure it's consistent. |
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Posted: 3/1/2019 3:50:35 PM EDT
[Last Edit: popnfresh]
[#26]
How do you know what the correct output is?
There is no JBM app as far as I know. Shooter is $10 I think and is a much better interface than Strelok IMO. I Don't see a point in keeping a calculator that is only functional for some things. I suppose the 5 different applications I posted could be wrong in the same way. One way to find out, shoot and see. |
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Posted: 3/1/2019 4:25:06 PM EDT
[#27]
Quote HistoryOriginally Posted By popnfresh:
How do you know what the correct output is? There is no JBM app as far as I know. Shooter is $10 I think and is a much better interface than Strelok IMO. I Don't see a point in keeping a calculator that is only functional for some things. I suppose the 5 different applications I posted could be wrong in the same way. One way to find out, shoot and see. |
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CO, USA
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Posted: 3/1/2019 4:27:43 PM EDT
[Last Edit: phdog]
[#28]
Quote HistoryOriginally Posted By popnfresh:
How do you know what the correct output is? |
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Posted: 3/1/2019 5:10:52 PM EDT
[#29]
How do you know the output is correct is a good question. Let us know when you make the range and actually find what that data is when actually fired.
As for the apps, I only use my phone app for centerfire rifles so works great. If I need anything else like a rimfire then I use jbm and print it out. Don't shoot pistols past about 50-75 yards so no need for pistol data on them. |
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CO, USA
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Posted: 3/4/2019 5:11:25 PM EDT
[#30]
Heard back from Hornady.
This is something that the developers are aware of and they will have it fixed with an update that will be pushed out to users soon. |
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Posted: 7/8/2019 10:55:17 AM EDT
[#31]
@LRRPF52 Will be able to explain this alot better than I can so I won't even try. But twist rate does effect ballistic coefficients.
http://bulletin.accurateshooter.com/2017/04/new-spin-on-bc-how-barrel-twist-rates-affect-bullet-drag/ A good article on this. |
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Posted: 7/8/2019 11:36:39 AM EDT
[Last Edit: popnfresh]
[#32]
Quote HistoryOriginally Posted By MDStroup:
@LRRPF52 Will be able to explain this alot better than I can so I won't even try. But twist rate does effect ballistic coefficients. http://bulletin.accurateshooter.com/2017/04/new-spin-on-bc-how-barrel-twist-rates-affect-bullet-drag/ A good article on this. Twist rate has no effect on drop of 100% stable bullets. |
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