Thread: calculator able to predict projectile pass height over variuis distances

I have a dilemma.

The maximum range that i can sight my rifle into, is on a range that has shooting positions that end at a maximum distance of 368 mts . The "100 yd" position is actually at 91 metres .
So my rifle is sighted in at 91 mts .
I need to shoot to 600 mts
what height above the bull ( on the 91 metre target ) should my projectile strike in its trajectory to a 600 mt distance target ?
I can dial up the 600 mt range on my scope and for the projectile ( 175 gr eldx 7mm ) at 2950 ft/sec , the up is 51 clicks .
the projectile then passes thru the 91 mt target . 33.5 cm above the bull .

these things are true
the target distance ( and zero distance ) is 91 mts .
the projectile is 175 gr eldx , G7 0.3470 , L=39.8 mm ( in 7mm prc case )
the velocity is measured at 2950 ft/sec
the rifle is 7mm prc at 1:8 twist
the weather is 20 cel , and no wind
the altitude is 60 ft above sea level
the humidity is 60%
the scope is swarovoski z5 3.5-18 ( click value 0.7 cm or 1/4 inch )
Strelock says 51 clicks up from 91 mt zero
swarovski says 51 clicks as well
the projectile strikes high at 33.5 cm above the bull on the 91 mt target when dialed up 51 clicks

what calculator is available to enter the data i have , to confirm the apparent trajectory and strike on the 91 mt target, is likely correct for a strike on the 600 mt target ?

cheers
les

Hi Les
Can you get a 20MOA angled rail? i would do this as its not just for optical clarity. Last weekend a mate was shooting his scope that was wound out all the way like you were describing. It broke.
So i would say this isn't the best idea imo.

But as per your original question, i use Chairgun Elite (android) and Applied Ballistics. Both can tell you in milrads what your holdover angle is (and that will be true at any range). so if it says 40clicks Elev for 600m, this will be roughly 40cm above zero at 100m. Slightly more for your reduced range. I'm guessing 44??

Tim

1. 91 metres is about 100 yards.

2. It appears that you are wanting to shoot at 91m, to check that your adjustment for a 600m shot is correct. There are 2 parts to this:
a) has the scope adjusted the point of impact by the correct amount as per the ballistic calculator solution? This is simple to check - what is the value of 51 clicks at 91m? Assuming a standard 1/4moa at 100y click - .25 inch*51; convert to mm - this is 32.385cm which is probably close enough to your 33.5cm to say that yes, the scope clicks adjust approximately correctly within the noise of the system limiting your ability to measure it accurately. You shouldn't be surprised to get 1cm or more of noise in your POI at 100m the way the vast majority of hunters zero).
b) Is the ballistic calculator solution correct to actually hit a target at 600m? You need to shoot at 600m to check this.

If the solution is not actually correct at 600m, you will need to check a variety of things to understand why. It also depends on the definition of correct - do you need to make a first round hit on small target, or is "getting on paper" acceptable?
1. Do you have a solid zero - i.e. a large enough sample size of shots in your zeroing process to have a clear picture of what your real mean point of impact is?
2. Is your velocity measurement accurate? Was it measured with a reliable instrument used correctly, and do you have a large enough sample size of shots to have an accurate mean velocity?
3. Do you have a large enough sample size of shots at 600m to say with confidence that the ballistic calculator solution is actually incorrect?
4. Is your scope height over bore measured and entered correctly?
5. Is the target actually at 600m or is there ranging error?
6. Is there a shooting incline?
7. Are all environmental factors measured and input accurately?

thanks for your input
the key is here is that i dont have access to a 600 mt range to confirm the scope setup , but i am going to a site that has up to 600 mts shots occassionall so i am wanting to be prepared before i get there .
i can confirm the following as accurate
the velocity . i make the ammunition and measure the speed ( over 100 rnds )
the target distance is 91 mts ( 100 yards )
I do not have acceess to a range that has a 600 mt mound and butt , hence the theoretical and practical testing at 91 metres . None of the ammunition has actually been fired onto a 600 mts target
the scope height is 1.85 inch above the bore .
the rifle shoots 1/2 groups .

I am fairly carefull to collect legitamite enviromenat conditions , so the weather statement is reliable as well .
I am pleased that the elevation adjustment looks to be correct for the scope adjustment at 51 clicks .
However the question remains , if the projectile i have described , and motivated to 2950 ft/sec , passes 33.5 cms high about the 91 metre target, will the arc of the trajectory, see the round fall into a circle of 12 inches at 600 mts ?

cheers
les

hold line caller will post you link


https://www.huntingnut.com/index.php...intBlankOnline

thanks for your input .
did you buy the applied Ballistics program? ( i see its a price of 200 USD ) or is there a cheaper way of getting use of it ?
I am a iphone guy so am having getting the android equivalent of the chairrgun elite
cheers
les

poke in your figures.... and look at rusults..you can change them as often and as much as you like till satisfied with answer. that one is free

Originally Posted by LJPRMC

thanks for your input
the key is here is that i dont have access to a 600 mt range to confirm the scope setup , but i am going to a site that has up to 600 mts shots occassionall so i am wanting to be prepared before i get there .
i can confirm the following as accurate
the velocity . i make the ammunition and measure the speed ( over 100 rnds )
the target distance is 91 mts ( 100 yards )
I do not have acceess to a range that has a 600 mt mound and butt , hence the theoretical and practical testing at 91 metres . None of the ammunition has actually been fired onto a 600 mts target
the scope height is 1.85 inch above the bore .
the rifle shoots 1/2 groups .

I am fairly carefull to collect legitamite enviromenat conditions , so the weather statement is reliable as well .
I am pleased that the elevation adjustment looks to be correct for the scope adjustment at 51 clicks .
However the question remains , if the projectile i have described , and motivated to 2950 ft/sec , passes 33.5 cms high about the 91 metre target, will the arc of the trajectory, see the round fall into a circle of 12 inches at 600 mts ?

cheers
les

1. 1/2 groups for how many shots? Unfortunately the reality is that a, or a series of, 1/2 inch 3 shot group provides imprecise information about your mean point of impact and you can expect "noise" in your down-range results as a consequence. 5 shots is little better.
2. There is no way to know whether a predicted solution from a ballistic calculator will allow you to hit a target at an extended range without actually shooting at that range. You can check that your scope will track the correct adjustment to apply the solution, but you cannot test the validity of the solution at 91m.


What kind of targets are you hoping to shoot at 600m?

you always have to shoot at and at least 1/3rd further then the shot you would take on an animal.
if you speed is from the box then take about 150 - 200fps off it especially if its Hornady

Originally Posted by Micky Duck

hold line caller will post you link


https://www.huntingnut.com/index.php...intBlankOnline

I have frollowed the link ... and downloaded the app .... looks like this could be what i am after
thanks
les

The AB computer programming is $200 the app should be $40. Hornady 4dof is free.

Your best bet is:
1. Confirm zero and muzzle velocity
2. Tall target test
3. Shoot as far as you can ~368m.

Originally Posted by gimp

1. 1/2 groups for how many shots? Unfortunately the reality is that a, or a series of, 1/2 inch 3 shot group provides imprecise information about your mean point of impact and you can expect "noise" in your down-range results as a consequence. 5 shots is little better.
2. There is no way to know whether a predicted solution from a ballistic calculator will allow you to hit a target at an extended range without actually shooting at that range. You can check that your scope will track the correct adjustment to apply the solution, but you cannot test the validity of the solution at 91m.


What kind of targets are you hoping to shoot at 600m?

Thanks for your input
do you use Gordons reloading tool ?
I can send you the typical results for the load including the shot group image and calculation
I shoot 3 rnd groups ( because the rifle is a sporter and the barrell heats up real quick and acccuraccy drops away )
I have a big black stag in mind that keeps showing himself 600 mts away across a farm ...

Within the limits of what you have to work with, there is one practical test you can do that will partly answer what I think is the main question you are trying to answer.

1. Sight rifle in for whichever your normal zero distance is. (Let’s say 91m/100yd)

2. Enter the ballistic data into the app for a (368m/400yd) shot. Dial according to the app data and shoot a group at this distance.
If the group is level with the aiming point, you can have a reasonable degree of confidence in data and dial at further distance. If it is not level, the next step is to work out if this is due to dial, calculator, other, or some of each.

To answer the question at the end of your post, the two ballistic calculators that you have used should both be able to reverse engineer your data if you enter a 600m zero and then look at the trajectory chart. Allow for some dispersion due to scope height etc but it should give a 91m/100yd elevation of ~33.5cm if your original calculation for a 600m dial up was based on a dial starting point of 91m/100yd.
Also note that the math only proves the math. If the math indicates the same elevation through two separate mathematical methods, it doesn’t prove what will happen in practice it only proves that both methods are as valid as each other.

The only way to know if your figures are right at 600m is to put some rounds down there. Theory is great and a good starting point, but the ballistics calculator is reliant on the operator making some decisions and a couple of wild arsed guesses on the way to the solution. One of these is the ballistic model or coefficient of the projectile, which is a measure of how quickly it bleeds energy off and loses speed as it travels and to a lesser extent how much it is affected by environmental factors. At 600m a small error in the calcs can turn a swing into a miss, or worse a badly hit animal.

It's not a factor of rifle or shooter, its just the way the apps work and the decisions you have to make when feeding the info in. The only way you are going to know if the solution is good is to put rounds where the solution tells you and see if they arrive at the predicted point of impact. There just isn't any other way, shooting at 100yds only just doesn't give you enough info to confirm what will happen further out, you have to get to somewhere you can stretch the legs.

A couple of times I've done this it's been spot on, more often there is an error somewhere which is either the ballistic coefficient is entered wrong, the wrong bullet is being used for the calculation, the velocity is not correct, or something else is out of thwack. One notable one, the bullets were impacting into the dirt about a meter below the target. Chrono was up the crap and telling porkies to the tune of around 500fps and the bullet selection was wrong in the app leading to a very incorrect solution. That combination of ammo and rifle was no good at longer ranges, despite everything indicating it was. One of those 'slow barrel' cases.

Not sure if this is relevant to what you are doing but to quote NZ Hunter (the Duleys), when referring to the 2.4-12x Z5,
"It shifted .975 inches at 100 yards for 4 clicks, just as all the other Z5s do".