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

Originally Posted by Shearer

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".

was the same with the older bushnell elite 6500's not moa but all the same might have been 1" at 100y

IPHY and there's a setting for that in most apps. Inch Per Hundred yards and use an elevation adjustment factor of 1.025

Originally Posted by No.3

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.

thanks for the insight ... some of which i have already experined myself.

Originally Posted by Shearer

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".

that sounds about right to me , because the z5 is described as 0.7cm per click at 100 metres, which would be 91mts/100 mts x 0.7cm per click for 100 yds . So the click value would equal about 0.63cm . the Duleys measurement is equal to 0.62 cm . in my measuring that would equal a blondie .

Originally Posted by Micky Duck

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

I have hooked up with the app ... so far looking good .

Originally Posted by T.FOYE

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

yep , i can get a 20 moa rail . and i have considered that as a solution to save some clicks and not max out all the scope has .

Yep all Swaro I’ve owned (Z3 & Z5 ) dial 0.975in at 100yds, or that damn close to that it does not matter. So you’d need to allow for scope dialing 0.975 rather than 1.05in in true moa. Obviously the further out you go the bigger the difference. Also consider that your measured muzzle velocity is derived from a Chrony, which like any measuring device has a level of precision or accuracy. It might be +\- 1-2% ? To validate your muzzle velocity you need to check drop at 600 or 700 yds, or further if possible. I doubt you’d see the difference at 400yd.

Greetings @LJPRMC,
I think we tend to over complicate things. I had just this need before I shot my first 600 yard shoot last year. I had the chronographed velocity for my load so just ran the trajectory using the Hornady on line software in 25 metre steps out to 600 metres, 600 yards is very close to 550 metres. Next I made a tall target with a NZDA 100 metre target taped on the bottom and the predicted 200 metre POI marked on it. The rifle was zeroed aiming at the bottom target with the shots falling on the upper mark. This was done on my home 200 metre range. The first shot at 600 yards was a 4 and the Target software validated my predicted velocity at that range.
I find the fascination with zeroing rifles at 100 yards or metres hard to understand. For bush hobbits this is likely fine but for rifles that will be used at longer ranges surely 200 metres would be a better option. My hunting rifles (regrettably hunting in name only these days) are zeroed at 200 metres or whatever range the MRT is 50mm or less. I see that your most often used range runs from 90 metres to a max of just over 350 metres. A base zero at 200 metres would extend your just shoot range considerably for a rifle in the 7mm Rem Mag class.
Regards Grandpamac.

An accurate zero is important if you aim to make first round hits on targets at longer ranges as frequently as possible.

Zeroing is simply having a clear understanding of where your point of impact is, in relation to your point of aim, and ensuring that it is satisfactory for your requirements.

Zeroing at 100m is easier to do accurately than 200m. Environmental factors causing noise in your data are less of an issue - aside from the logistical concerns of 200m range availability, etc.

Zeroing POI to be on POA at 100m, rather than some offset, is in my opinion preferable - A precise zero on POA at 100m doesn't prevent you from dialling up .5MIL when walking around to have a "PBR" for hunting practically.

It is important to be clear that there is a difference between zeroing AT 200m, vs zeroing FOR 200m.

One is completing the task of data collection at that range, the other is making a sight adjustment for POI/POA co-incidence at that range.

My advice is the black stag will have to walk this time.

By all means put up a paper plate where he comes out and give it a go.

You can use the jbm web site for a very good calculator. Call me paranoid but i see on phone ballistic apps as a security risk and try to choose my supplier thoughtfully.

If you are truing your app data at the actual shooting distance (+30% would be better as suggested) then there are several potentially significant pieces of data you need to record at the time if you want the app to predict successfully in slightly different conditions:
Range and slope
Air temp and ammo temp (could be the same if you’re careful)
Barometric pressure where you’re shooting ( station pressure)
Wind and direction
Changes in BC at different velocities (see Litz data if possible)

Less criti al are:
Humidity
Direction ( azimuth by compass) and latitude/longitude.

For a good explanation of these try and get a copy perhaps pdf of Brian Litz Applied Ballistics for Long Range Shooting.

You will need to let your barrel cool and get at least 5 shots per group, plus confirm stability from one session to another transported in case, cleaned and so on , the confirm your sight adjustments which you can do in a box test at 100 yd but of course you need 5 good shots at zero and plus 30cm.

For a Fallow you are looking for a stable zero and a solution on the day within < 0.1 mRad (6cm at 600m) to allow space for other variations that do accumulate. Sounds like you have the common sense and the gear to do it if you dont rush.

Thank you all for your input. your help has led me to the calculator i was after .
Here's an update: The rifle is a "light sporter" in 7mm PRC with a fluted barrel. Three rounds are enough to heat it up and cause shots to deviate. Therefore, cooling is essential (I use a battery-powered air mattress pump and garden hose). The rifle isn't PRS grade, but it consistently groups three rounds within 3/4 MOA (the fourth could land anywhere).

Realistically, I'm aiming for a single bullet to hit within a 30 cm diameter circle at 600 meters. In today's test, I managed to place two rounds within a 100 mm circle at 368 meters (400 yards). I saved the third round for a single shot at a tall target, then adjusted by 51 clicks to hit a 600-meter target. The last round struck 60.5 cm above the 368-meter aim point.

The round traveled downrange at 2955 ft/sec. The calculator predicted it should have hit 71.5 cm above the aim point to reach the 600-meter target. However, it hit at 60.5 cm. So, with only one round to consider, I'm 11 cm low, but I'm not reading too much into that. It's likely a result of various factors. After all, how likely would it be to hit exactly at the 71.5 cm mark?

Originally Posted by LJPRMC

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

Thank you all for your input. your help has led me to the calculator i was after .
Here's an update: The rifle is a "light sporter" in 7mm PRC with a fluted barrel. Three rounds are enough to heat it up and cause shots to deviate. Therefore, cooling is essential (I use a battery-powered air mattress pump and garden hose). The rifle isn't PRS grade, but it consistently groups three rounds within 3/4 MOA (the fourth could land anywhere).

Realistically, I'm aiming for a single bullet to hit within a 30 cm diameter circle at 600 meters. In today's test, I managed to place two rounds within a 100 mm circle at 368 meters (400 yards). I saved the third round for a single shot at a tall target, then adjusted by 51 clicks to hit a 600-meter target. The last round struck 60.5 cm above the 368-meter aim point.

The round traveled downrange at 2955 ft/sec. The calculator predicted it should have hit 71.5 cm above the aim point to reach the 600-meter target. However, it hit at 60.5 cm. So, with only one round to consider, I'm 11 cm low, but I'm not reading too much into that. It's likely a result of various factors. After all, how likely would it be to hit exactly at the 71.5 cm mark?

The reason long range rifles are zero'd at 100m is to ensure that all your likely ranges will be holdover (not a mix of plus and minus). Not counting the first 25m or so.
FT airguns are setup in a similar way to avoid accidentally winding your scope the wrong way. They normally zero at 25m as their trajectory pretty much hits the line of sight and doesn't create 2 point blank moments.

Originally Posted by LJPRMC

Thank you all for your input. your help has led me to the calculator i was after .
Here's an update: The rifle is a "light sporter" in 7mm PRC with a fluted barrel. Three rounds are enough to heat it up and cause shots to deviate. Therefore, cooling is essential (I use a battery-powered air mattress pump and garden hose). The rifle isn't PRS grade, but it consistently groups three rounds within 3/4 MOA (the fourth could land anywhere).

Realistically, I'm aiming for a single bullet to hit within a 30 cm diameter circle at 600 meters. In today's test, I managed to place two rounds within a 100 mm circle at 368 meters (400 yards). I saved the third round for a single shot at a tall target, then adjusted by 51 clicks to hit a 600-meter target. The last round struck 60.5 cm above the 368-meter aim point.

The round traveled downrange at 2955 ft/sec. The calculator predicted it should have hit 71.5 cm above the aim point to reach the 600-meter target. However, it hit at 60.5 cm. So, with only one round to consider, I'm 11 cm low, but I'm not reading too much into that. It's likely a result of various factors. After all, how likely would it be to hit exactly at the 71.5 cm mark?

I'm not sure that you're clear about what you're trying to achieve.

You seem to be wanting to confirm that the output of a ballistic calculator will allow you to hit a deer at 600m.

The approach you are taking doesn't really give you the ability to know this.

Confirmation that the ballistic calculator solution matches reality requires shooting enough shots on targets at long enough range for errors to be detectable and have confidence that the error is real and not random variation. The magnitude of any errors in the ballistic calc at 368m will be very small.

The current approach mainly gives you a poor test of the straightness and value of your scope clicks.

Originally Posted by gimp

The current approach mainly gives you a poor test of the straightness and value of your scope clicks.

I get what your driving at completely.........
so the mathimatition inside me says...if your 51 clicks wasnt enough by say???1/6th if you add 1/6th amount of clicks you should in effect be correct now elevation wise.... IF that works you SHOULD in futre know that for EG instead of ten clicks you need to stick in 12....and try it
by doing so you remove any error in the dialing