Ballistic apps and potential energy via gravity

[Stubbers]

I appreciate that, as I am invested (time and use) in Strelok. Unfortunately, I’m currently using an iPhone so I do not have access to any updates of Strelok. Though I continue to use Strelok with the hopes that updates will be more readily available in the USA in the future.

Strelok has some other minor data errors that I’d like to see fixed as well. It’s internal data is done in meters, but when displaying yards, internally it rounds (always up) to the meter. That causes some impossible results. Small but minor errors that bug me none the less.

As I said, I’m not going to put any time into trying to get Hornady to fix their app. I’d rather stick with Strelok, especially if Igor continues to update it. And I’ll switch to a Samsung device if that means I can get updated Strelok versions.

Hornday is to prove the effect. You could also just use its data as reference on your +/- angle difference provided you put in your inputs correctly. ..something is better than nothing.

If you're looking for a ballistic app with 0 errors, we're not quite there yet, you'll need to make custom dope cards.

-Matt

 

[Caliber 22]

And I’ll switch to a Samsung device if that means I can get updated Strelok versions.

I use an Android phone but the only way to "update" is to buy a new copy from the Huawei site. Since most of his update of late was additions of reticles and ammo I am not to eager to update. What is in the app now works for me together with the other apps I have. I only use it occasionally anyway.

 

[Scotchmo]

I use an Android phone but the only way to "update" is to buy a new copy from the Huawei site. Since most of his update of late was additions of reticles and ammo I am not to eager to update. What is in the app now works for me together with the other apps I have. I only use it occasionally anyway.

I see a lot of new reticle requests on the Strelok Facebook page. I don’t really care about reticles as I only need the numerical data for compensation.

I use Strelok a LOT!

I have a Bluetooth MTC rangefinder, Bluetooth Kestrel weather station, and a Bluetooth anemometer, all purchased because they communicate with Strelok. The real time compensation adjustments in Strelok are valuable when shooting long distance. I don’t really want to give those up if switching to another app. I don’t mind purchasing Strelok again.

 

[steve123]

Aside from the ballistic apps and angles I've experienced some crazy vertical problems when shooting long range with very precise centerfires.
I would use a Kestrel and DA/Density Altitude.

My friends shooting range is up on a hill around 7 degrees from a steel Ram I was shooting 550 yards away. The wind was coming in to me at 20-25 ish mph. I normally hit this Ram no problem because it's a easy target. We're talking a 6mm 105gr/G1BC of .545 at 3120 fps. After missing high a half dozen shots I measured the misses to be averaging .5 mils high. I was shocked! So much so I couldn't resist going back later in the week in normal winds to try again only to have my dope right on as usual.
The only conclusion that made sense to me was that this topography combined with wind pressure pushed the bullets up when the wind hit the hill.

I also had what must have also been wind affecting vertical at our AZPRC long range centerfire matches which was high above the valley below where the steel was. We knew the distances were correct because my engineer friend used a fancy GPS unit he had for his work that supposedly was precise to 10mm. If it was windy we could see the difference between our dope and how much compensation vertically we'd need to hit the steel.

Airgun related, our FT club had some targets at steep angles down into a gravel pit. I could compensate pretty closely for the angle when it was calmish but the pellet was going crazy in the vertical when it was windy. People already knew to aim lower because of the down angle but the patterns of misses on the faceplate when it was windy proved that the topography was pushing the pellet way way up. Say at 55Y to make a hit one would need to aim a half inch below the KZ and 2.5"-3" off of it vs the normal lower half of the KZ and a 1/4" out of the KZ.

And shooting my Vulcan 3 using Altaros slugs when it's windy but this time shooting uphill at 13 degrees on windy days at 300Y I notice the vertical fall apart as well. The vertical can be almost twice what it is on calm days.

All can be pretty frustrating, lol.

 

[Stubbers]

I just checked, and GeoBallistics ALSO calculates this effect and is free to try but pro cost 15$. Works with Kestrel Weather Station and WeatherFlow.

I entered in the same Data as the above Real world test, and it actually is closer than Hornday @ .4"~ predicted difference from 1300 fps 240 gr @ -15/+15....

If you have YOUR slug information from BC (G1 or G7), Diameter, Length, and Muzzle velocity, and weight, I can see what it spits out @ +15 and -15 for you.

-Matt

 

[Scotchmo]

Aside from the ballistic apps and angles I've experienced some crazy vertical problems when shooting long range with very precise centerfires.
I would use a Kestrel and DA/Density Altitude.

My friends shooting range is up on a hill around 7 degrees from a steel Ram I was shooting 550 yards away. The wind was coming in to me at 20-25 ish mph. I normally hit this Ram no problem because it's a easy target. We're talking a 6mm 105gr/G1BC of .545 at 3120 fps. After missing high a half dozen shots I measured the misses to be averaging .5 mils high. I was shocked! So much so I couldn't resist going back later in the week in normal winds to try again only to have my dope right on as usual.
The only conclusion that made sense to me was that this topography combined with wind pressure pushed the bullets up when the wind hit the hill.

I also had what must have also been wind affecting vertical at our AZPRC long range centerfire matches which was high above the valley below where the steel was. We knew the distances were correct because my engineer friend used a fancy GPS unit he had for his work that supposedly was precise to 10mm. If it was windy we could see the difference between our dope and how much compensation vertically we'd need to hit the steel.

Airgun related, our FT club had some targets at steep angles down into a gravel pit. I could compensate pretty closely for the angle when it was calmish but the pellet was going crazy in the vertical when it was windy. People already knew to aim lower because of the down angle but the patterns of misses on the faceplate when it was windy proved that the topography was pushing the pellet way way up. Say at 55Y to make a hit one would need to aim a half inch below the KZ and 2.5"-3" off of it vs the normal lower half of the KZ and a 1/4" out of the KZ.

And shooting my Vulcan 3 using Altaros slugs when it's windy but this time shooting uphill at 13 degrees on windy days at 300Y I notice the vertical fall apart as well. The vertical can be almost twice what it is on calm days.

All can be pretty frustrating, lol.

I’m not sure if Strelok correctly takes into account the lift or depression on projectiles when shooting at high angles into or away from a horizontal head wind/tail wind/quartering wind. That’s a whole other issue.

 

[Scotchmo]

I just checked, and GeoBallistics ALSO calculates this effect and is free to try but pro cost 15$. Works with Kestrel Weather Station and WeatherFlow.

I entered in the same Data as the above Real world test, and it actually is closer than Hornday @ .4"~ predicted difference from 1300 fps 240 gr @ -15/+15....

If you have YOUR slug information from BC (G1 or G7), Diameter, Length, and Muzzle velocity, and weight, I can see what it spits out @ +15 and -15 for you.

-Matt

Thanks Matt,

I already put it into the Hornady app, and for horizontal shots, it is close to Strelok and real world. But the 15 degree angle shots are way low for the needed compensation at 600yds.

Even though the overall compensation shows low, the difference between up and down in the Hornady app looks to be about what I would expect, so I could use that to adjust the compensation that I get from Strelok. But that’s one more thing I’d rather not have to do in the moment.

Here is MY slug information for the current highest BC airgun projectile that I use:
G7 BC=0.182
.307” at max diameter (driving band)
1.078” long
1010fps
171gr

 

[Stubbers]

Thanks Matt,

I already put it into the Hornady app, and for horizontal shots, it is close to Strelok and real world. But the 15 degree angle shots are way low for the needed compensation at 600yds.

Even though the overall compensation shows low, the difference between up and down in the Hornady app looks to be about what I would expect, so I could use that to adjust the compensation that I get from Strelok. But that’s one more thing I’d rather not have to do in the moment.

Here is MY slug information for the current highest BC airgun projectile that I use:
G7 BC=0.182
.307” at max diameter (driving band)
1.078” long
1010fps
171gr

Geoballistic shows 23.8" or 1.1 mrad predicted difference at 600 yards, assuming 100 yard zero.

-Matt

 

[Stubbers]

Using the same data in Hornady, it shows 24.7" difference between -15 or + 15 at 600 yards with 100 yard zero.

Seems both calculators are really close...within 1"...and there could be a small discrepancy due the rounding of mrad to the 1st decimal.

Also Hornady can pair with weather meters as well via bluetooth, just as Geoballistics and Sterlok.

239 VS 222 FPE @ target shown via Geoballistics
242 VS 227 FPE @ target shown via Hornady

-Matt

 

[Scotchmo]

Geoballistic shows 23.76" or 1.1 mrad predicted difference at 600 yards, assuming 100 yard zero.

-Matt

40 yd zero
82F
28.74 inHg
55% humidity
600yds

Strelok
-15 degrees, 99.7 moa
0 degrees, 103.7 moa
+15 degrees, 99.7 moa

Hornady
-15 degrees, 91.01 moa
0 degrees, 103.65 moa
+15 degrees, 95.14 moa

I think the difference between the 91 and 95 Hornady values might be about right, but they are way too low to be on target. Strelok does not differentiate between + or - 15 degrees, but the 99.7 value gets me close and sometimes on target.

What are the MOA compensation values for Geoballistics?

 

[Stubbers]

Geoballistic, assuming 1.75" scope height.

-15 = 99.3 moa
0 = 105 moa
+15 = 103 moa

-Matt

 

[Scotchmo]

Geoballistic, assuming 1.75" scope height.

-15 = 99.3 moa
0 = 105 moa
+15 = 103 moa

-Matt

2.76” is the scope height. Even so, the Geoballistics predictions look pretty good. A lot better than Hornady.

 

[Stubbers]

2.76” is the scope height. Even so, the Geoballistics predictions look pretty good. A lot better than Hornady.

Going from 1.75" to your 2.76" with Geoballistic (found where I can let it round to 2nd decimal vs 1st)

-15 = 97.03 MOA
0 = 102.78 MOA
+15 = 100.75 MOA

 

[Stubbers]

Igor replied to my request and said "I will think how it can be done"....because (in my opinion) integrating such effects is not straightforward and the current apps that achieve this calculation probably relied on Doppler data to work out a expression or equation that lines up with their data. Wish I had the answers for him because it's not that he isn't willing, rather the solution isn't known or widespread knowledge, and heck, I'd like to integrate it into my personal one but...math is hard.

-Matt

 

[Scotchmo]

Igor replied to my request and said "I will think how it can be done"....because (in my opinion) integrating such effects is not straightforward and the current apps that achieve this calculation probably relied on Doppler data to work out a expression or equation that lines up with their data. Wish I had the answers for him because it's not that he isn't willing, rather the solution isn't known or widespread knowledge, and heck, I'd like to integrate it into my personal one but...math is hard.

-Matt

I don’t see why it would take a Doppler data.

There is a gain or loss in projectile energy as the target elevation is raised or lowered. Very easy to calculate that. Since I would be hard pressed to do the analytics, I would be using numerical integration, probably every inch (or cm).

Over the entire distance of 600yds, when compared to a level shot, the 171gr projectile loses about 11.4 additional FPE on a +15 degree shot and gains that amount on a -15 degree shot. Those losses or gains can be factored in incrementally along the trajectory path, and the corresponding velocity adjusted accordingly.

There is also the air density changes that must be accounted for as the projectile rises or falls. That can also be accounted for incrementally via numerical integration.

It’s not an exact solution, but probably better than ignoring it.

 

[Stubbers]

I don’t see why it would take a Doppler data.

There is a gain or loss in projectile energy as the target elevation is raised or lowered. Very easy to calculate that. Since I would be hard pressed to do the analytics, I would be using numerical integration, probably every inch (or cm).

Over the entire distance of 600yds, when compared to a level shot, the 171gr projectile loses about 11.4 additional FPE on a +15 degree shot and gains that amount on a -15 degree shot. Those losses or gains can be factored in incrementally along the trajectory path, and the corresponding velocity adjusted accordingly.

There is also the air density changes that must be accounted for as the projectile rises or falls. That can also be accounted for incrementally via numerical integration.

It’s not an exact solution, but probably better than ignoring it.

If you don't see why, please provide the math needed here mate. Otherwise, maybe you don't see why because you don't comprehend why...

A lot of math is derived from data collected by instruments such as Doppler radar, which many modern ballistic formulas are based on...

-Matt

 

[Scotchmo]

If you don't see why, please provide the math needed here mate. Otherwise, maybe you don't see why because you don't comprehend why...

A lot of math is derived from data collected by instruments such as Doppler radar, which many modern ballistic formulas are based on...

-Matt

I comprehend it and I see why some might think they need that data.

As I said, I would not attempt to do the analytical integration, because as you said “math is hard”. Well, at least calculus is hard. That’s why I would use numerical integration. So instead of solving for some complex integral, it only requires a relatively simple formula that can be more easily implemented using a numerical solution of sufficiently small increments.

delta(FPE)=sin(angle) x grains/7000 x increment

Here is a simplified example for a single segment where the trajectory angle is 15 degree. For further simplification, I’ll use 1 foot for the increment, rather than 1in (or 1cm).

delta(FPE)=sin(15) x 171gr/(7000gr/pound) x 1foot

So for every foot of travel closer to the target, 0.063fpe is added (or subtracted) to/from the energy balance of the projectile.

The result is that the projectile will slow down a little faster on an inclined shot. And just the opposite for a decline shot.

As pointed out earlier, this will be partially counteracted by the changing density, which should also be included in the numerical integration. But I would guess, for most cases, that over half of that potential energy to/from kinetic energy conversion would show up as a corresponding increase or decrease in projectile velocity at the target.

 

[Stubbers]

I did the math...my ballistic solver now includes this effect. I also added in spin drift (active in below calcs), Coriolis and Eotvos effect (disabled), and magnus effect (disabled). However I am not currently calculating density change along the trajectory because you'd have to shoot at very steep angles, nearly like a rocket, to get substantial density change, however that is my next step...because I like challenges.

*Edit* Added tracker to density changes over the trajectory for every 50 feet, which effects which reference law is taken from the drag tables.

I even allow you to include the wind in your zero in case you're zeroing in the wind at your zero, which I don't think most ballistic solvers allow you to include. Took me about 3 days to convert my old ballistic solver that used constant cD to one that uses current cD values provided by Ballistic Boy.

Shown below is -10degree, 0 degree, and +10 degree with a 33.95 traveling 876 fps, 500 yards, 10 yard zero.

Even predicts the changes in FPE just as well.

-Matt

 

[JungleShooter]

I did the math...my ballistic solver now includes this effect. I also added in spin drift (active in below calcs), Coriolis and Eotvos effect (disabled), and magnus effect (disabled). However I am not currently calculating density change along the trajectory because you'd have to shoot at very steep angles, nearly like a rocket, to get substantial density change, however that is my next step...because I like challenges.

*Edit* Added tracker to density changes over the trajectory for every 50 feet, which effects which reference law is taken from the drag tables.

I even allow you to include the wind in your zero in case you're zeroing in the wind at your zero, which I don't think most ballistic solvers allow you to include. Took me about 3 days to convert my old ballistic solver that used constant cD to one that uses current cD values provided by Ballistic Boy.

View attachment 501442

Shown below is -10degree, 0 degree, and +10 degree with a 33.95 traveling 876 fps, 500 yards, 10 yard zero.

View attachment 501432


View attachment 501434
View attachment 501436
View attachment 501438


Even predicts the changes in FPE just as well.

-Matt

Wow!
Matt, that is a loud, approving WOW that's coming from my airgunner's soul....!

So glad there are people who are not like me (they did not flunk physics and are able to do mental miracles like you)!


Of course, now we all want your program/app!!
For iPhone, Android, Mac, and Windows. Linux maybe, too.
We can never get enough! (n + 1 applies to everything....)


Matt, rock on, calculate on, shoot on!

Matthias

 

[Scotchmo]

I did the math...my ballistic solver now includes this effect….

-Matt

That’s good. I’m curious what approach you took. Solving for the integral or numerical integration as I would do? And did you use the potential energy conversion to/from kinetic energy?