Thread: Trajectory calculation issue

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?

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!