Trajectory calculation issue

While at the long range shoot in Kurow we had the opportunity to confirm our drop charts and collect some real data. I got the following real world results (all in yards because 1000 yards sounds way cooler than 900m) rifle is zeroed at 100m (110 yards)
343 - 4moa
480 - 8.5 moa
568 - 11.25 moa
697 - 15 moa
850 - 20 moa
5 degree angle
7mm mag firing 168gr berger vlds at 2960 fps (thats what chrony told me but 2900 seems to replicate the trajectory better)
I am using shooter and having issues getting the numbers to align to the real world results. Anyone want to join me in trying to get things to line up?
The frustrating thing is my other 2 rifles are spot on straight from shooter so think something must be wrong with the input data.
Might have to go and do another long range dady and do the data collection again to confirm but it was all pretty convincing on the day with shots landing as they should with the various corrections etc.
Wondering if maybe when we were ranging the steel targets we were actually getting readings off the ground in front/behind
Gimp did you measure the ranges to each plate from the plates at all? Did anybody else get different ranges for the plates?

where are you getting chrony data?

Are you using litz BCs?

I think you have sussed it already HH. Until you can confirm the ranges are correct you could be creating a larger problem.
How much different are the soloutions, more or less MOA? I use the same program (shooter)as well as JBM on my phone and can have them both open to compare. I sometimes get a slight difference but shooter seems the most precise. Thanks BB!
Ranging small plates without a background can be frustrating after a few rounds are wasted.
Accurate speeds, atmospherics and BC's are very important as well.

yeah I always range multiple ranges myself with my own gear... never use other guys data either..... you always seem to end up mucked up...

Special when kiwigreg tells you XY range and umm greg why am I 2m low?

Actually I had a rifle sighted in for 100yd but use meters for ranges soooo maybe if you check shooter settings and set the zero to 110 in the edit rifle data bit or better yet be less confusing and sight in for 100yd.... mine was alll way up the fuck when I had that... the other thing to make sure is right is correct sight height it can make a fair difference to (half bolt dia+half scope dia+distance between scope and bolt)

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Originally Posted by baldbob

yeah I always range multiple ranges myself with my own gear... never use other guys data either..... you always seem to end up mucked up...

Special when kiwigreg tells you XY range and umm greg why am I 2m low?

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Or um spotting for you and you wouldn't believe me you were 4-5m right of target! 3 or 4 shot later you realized you went wrong way with windage! shouldn't have brought this up I know after the incident up the river when I had lost my windage Zero but couldn't help myself :yaeh am not durnk:

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Originally Posted by veitnamcam

Or um spotting for you and you wouldn't believe me you were 4-5m right of target! 3 or 4 shot later you realized you went wrong way with windage! shouldn't have brought this up I know after the incident up the river when I had lost my windage Zero but couldn't help myself :yaeh am not durnk:

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Uh Oh!!! Your in the poos now :D

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Originally Posted by R93

Uh Oh!!! Your in the poos now :D

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Im waiting for the backlash:D

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Originally Posted by veitnamcam

Im waiting for the backlash:D

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If I know BB he's brewing a goody!!!! Or gone to bed :P

I can take it:D so can he:thumbsup:

Its true he had a serious issues with putting things sheeps bums that day.... :thumbsup:

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Originally Posted by baldbob

Its true he had a serious issues with putting things sheeps bums that day.... :thumbsup:

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:D:D

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Originally Posted by baldbob

Its true he had a serious issues with putting things sheeps bums that day.... :thumbsup:

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He is practically a Coaster then Adam? :yaeh am not durnk:

dammit you bet me to it:D

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Originally Posted by R93

He is practically a Coaster then Adam? :yaeh am not durnk:

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I must say he excelled at the initiation.....;)

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Originally Posted by baldbob

I must say he excelled at the initiation.....;)

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:thumbsup: I hope it doesnt mean we have to share hunting spots with him!

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Originally Posted by R93

:thumbsup: I hope it doesnt mean we have to share hunting spots with him!

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He snores very loud and farts alot in his sleep so im not looking forward to sharing a hut with him in may:omg:

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Originally Posted by baldbob

He snores very loud and farts alot in his sleep so im not looking forward to sharing a hut with him in may:omg:

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I noticed you stopped short of saying.......sleeping bag :o Oh where are WE going cuz? Tahr ballot? Or my spot to stewy?

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Originally Posted by R93

I think you have sussed it already HH. Until you can confirm the ranges are correct you could be creating a larger problem.
How much different are the soloutions, more or less MOA? I use the same program (shooter)as well as JBM on my phone and can have them both open to compare. I sometimes get a slight difference but shooter seems the most precise. Thanks BB!
Ranging small plates without a background can be frustrating after a few rounds are wasted.
Accurate speeds, atmospherics and BC's are very important as well.

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They are .75moa out around the mid range targets meaning it has a more pronounced curve than the ballistics programmes are calculating, think the ranges must be out, was using the little leica rangefinder and was hard to keep the dot on the target, should have used my bino range finders, would be 30 yards difference for the worst one to make the adjustments add up, at least that means I only need to re-test a target at that one range and that should tell me

Hori, here are the ranges I had, in Yards, Xs denote the plates :)
290 x
340 XX
471 XX x
564 XX
690 XXX
720 X
835 XXX
1050 XXX

We only shot at the last two, Norway shot at 690, with my rifles.

I found that speed is the variable I need to change the most to get things to "fit" better.

I usually take a few fps off what my cronie tells me & usually it's pretty close.

My 22-243 data must be bang on as I usually hit first or second everytime with it, the others except the 375 not so much to varing degrees......:(

A few things I always check/confirm if things aren't quite working out...
1. reconfirm zero, particularly if you are always shooting X clicks high/low consistantly
2. recheck data input, I once put the scope above bore height in the zero height field. Caused some head scratching after confirming zero... previous load had been spot on... I would check your zero range (as BB said), is it yards or metres, and should it be the other way round?
3. It could be BC related, are you using G1 or G7? Quoted BC's don't work in either my 338 or 7mm, both are pushing the projectiles out faster than the velocity range the BC's generally reflect, so the BC's I have settled on are higher

HH, I've had this occasionally as well & put it down to ranging errors. The ranges I noted were slightly different to yours.
355yds
476
602
680 (Plate just in from the gateway)
704 (plate in the Gut on the hill)
860
1070
I heard someone say they ranged the longest plates at 1050yd, we had 1070 & that's an extra MOA on for my girl gun.

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Originally Posted by horihunter

While at the long range shoot in Kurow we had the opportunity to confirm our drop charts and collect some real data. I got the following real world results (all in yards because 1000 yards sounds way cooler than 900m) rifle is zeroed at 100m (110 yards)
343 - 4moa
480 - 8.5 moa
568 - 11.25 moa
697 - 15 moa
850 - 20 moa
5 degree angle
7mm mag firing 168gr berger vlds at 2960 fps (thats what chrony told me but 2900 seems to replicate the trajectory better)
I am using shooter and having issues getting the numbers to align to the real world results. Anyone want to join me in trying to get things to line up?
The frustrating thing is my other 2 rifles are spot on straight from shooter so think something must be wrong with the input data.
Might have to go and do another long range dady and do the data collection again to confirm but it was all pretty convincing on the day with shots landing as they should with the various corrections etc.
Wondering if maybe when we were ranging the steel targets we were actually getting readings off the ground in front/behind
Gimp did you measure the ranges to each plate from the plates at all? Did anybody else get different ranges for the plates?

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Very interesting you should post this, as i have just been through the same process myself!

I struggled a bit to get my actual drops to match the numbers exactly, I played with 4 different ballistic programs, trajectory validation, BC, FPS, and even steeped BC's.

Lernt heaps about fudging charts and got heaps of advice from people that know their shit, and in the end i realised that what you are trying to achieve with a drop chart is to create numbers that match your ballistic curve as close as possible. You are talking about EXACT points at an EXACT distance, which may be a bit to much to ask for. Should however be possible to match most of them with a singe click out here and there.

Some important things to consider that will effect your numbers, especially at the range you are working to: You have to measure your EXACT scope height above bore, you have to make sure your scope clicks are exactly .25 MOA (if they are in MOA), you have to make sure you are not getting any backlash in your scope while shooting those groups - a good tip is to wind your scope up and down between each shot at the longer ranges, make sure your elevation and air pressure match your sighting in conditions.

I can have a play tonight with the numbers, need elevation, pressure, temp, scope height. Is your Zero EXACT in the bull or is it +- 1/2

As per another thread, this is also one of the reasons where it helps being able to shoot a small group at the longer ranges!

Any chance the scope is not dialing right?

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Originally Posted by outdoorlad

HH, I've had this occasionally as well & put it down to ranging errors. The ranges I noted were slightly different to yours.
355yds
476
602
704 (plates in the Gut on the hill)
Correction 748 (Plate just in from the gateway)
860
1070
I heard someone say they ranged the longest plates at 1050yd, we had 1070 & that's an extra MOA on for my girl gun.

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Correction to one of the distances.

Looking at my 602yd plate data shot it looks like we misranged that as I dialed for 600 & then needed to correct down 3/4 Moa for a centre hit which would equate to the dist KG & HH got & tie in nicely with my drop chart. (mystery solved)

scope height is 1.92"
pressure 986 hpa
I have reduced speed to 2890fps and can get it within .5moa of the real world figures now which may just be as close as I can get it. It ranges from .1 to .5 MOA low across the given ranges leaving a spread of .4, allowing for shooter error I might just add one click to the zero and should have it pretty close.
off to the range again tomorrow...

What time are you going out to the range?

So 986 was the absolute press for the altitude we were at? That would make it about 730ft above sea level, you've applied that correctly

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Originally Posted by horihunter

scope height is 1.92"
pressure 986 hpa
I have reduced speed to 2890fps and can get it within .5moa of the real world figures now which may just be as close as I can get it. It ranges from .1 to .5 MOA low across the given ranges leaving a spread of .4, allowing for shooter error I might just add one click to the zero and should have it pretty close.
off to the range again tomorrow...

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Had a quick play, I have dropped it to 2910 fps and tweaked the BC a bit and got it mostly to .25 MOA but I think the range at 568yards may be a bit suspect...

This is what I did if it helps..

BC 0.550
2920fps
730 ft
29 hg
Scope Height 1.8

340 - 4.25
480 - 8
568 (odd one) - 10.5 (sure that was not 590ish?)
700 - 14.75
850 - 20.25

I'm wodering if it should be 590is I see KG and I both had 564-568 while outdoorlad had 602... that would certainly help explain that one. Will try something at the same range again in weekend if all goes well

Check your chrony reading with someones chrony that is calibrated correctly, by placing it in front and behind yours. One should not smudge BC's to get things right the factories spend serious money establishing these figures.

How exactly is someone elses chrony 'calibrated correctly'
By firing a projectile of known velocity over it? then how is the 'known' velocity 'known'?? by being shot over a calibrated chrony?? (repeat the process)

Factory BCs are at XXX speed bracket.
If you are either side of that exact speed it was tested, the the BC is invalid as a given finite number - BCs are a curve - the number the factories supply is an average over a speed range and only fits that bracket even roughly. You can be either end of the bracket and the BC is different.
Same with G7, run it faster or slower than they dont fit.
These are facts not opinions and are almost 100 years old

Personaly id be more inclined to tweak the BC 1st before playing with the FPS (which may be a few FPS out but is still a known factor)

In this case HH has varified his drop at the longer ranges he will be shooting at which helps set the rest of the chart. (as long as he confirms that mid-range drop :thumbsup:)

Will be pretty hard if not impossible to match exactly, but tweaking the BC a bit can match the curve to .25 MOA, which interestingly enough is .25 UP and .25 DOWN some ranges, so the ballistic curve is running smack in the middle between what he shot on the forum range shoot.

:wtfsmilie: I wonder where that info came from.

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Originally Posted by Terminator

:wtfsmilie: I wonder where that info came from.

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Easy daisy ;)

This is slightly unrelated, but re: to measuring BC yourself from drops etc.

From Brian Litz' book:

175gr 7mm Sierra Matchking (random projectile selected) G1 BC measured with doppler radar

1500fps: .584
2000fps: .641 (.063 up from 500fps difference)
2500fps: .656 (.015 up from a 500fps difference)
3000fps: .677 (.021 up from 500fps difference)

Average over bullet flight from 1500-3000fps: .639

Points:
-I see no reason why the trend of "little variation for 500fps speed increase at higher speeds" wouldn't continue to be a similar negligible difference at 3000/3500fps.

-You will never be able to measure a difference in the real world from that sort of difference in BC, considering all the other factors and the error factor of the instruments you are using. A .1 difference in G1 BC gives you something like 2" different in drop at 500 meters. I challenge anyone who claims that their zero, data, shooting, scope tracking is perfect to the degree that they can accurately measure that sort of difference

-If you do have a higher initial BC, it will drop closer to the average anyway at the ranges where it becomes more relevant



I'm not saying anything about logging your real world observed results and trying to make them fit a ballistic calculation for the purposes of hitting stuff. Just saying that there are limits to the accuracy you an ascribe to field gathered data.

If you have a faulty chronograph, bad zero, scope that doesn't track correctly, bad range, bad shot, bad data input into calculator, bad data from weather meter, then your results from program may not line up properly. So log everything and simply work from your notes instead for data.

A note: I'm slightly drunk

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Originally Posted by baldbob

Actually I had a rifle sighted in for 100yd but use meters for ranges soooo maybe if you check shooter settings and set the zero to 110 in the edit rifle data bit or better yet be less confusing and sight in for 100yd.... mine was alll way up the fuck when I had that... the other thing to make sure is right is correct sight height it can make a fair difference to (half bolt dia+half scope dia+distance between scope and bolt)

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the difference for me between a 100m and 100y zero is .096moa, ie, too small to correct for

I don't remember the exact ranges from the shoot and I did not log anything because I have to change my load since it decided to start piercing primers after sitting in the sun all day.