Dope charts - what's your procedure w details

[djtjr]

Guys what are some of the tips and tricks you use in establishing your dope/drop charts? What are the details of your procedure from start to finish What are the variables you prefer to tweak to get theoretical drops to match up with field results. I feel like lately to get my field drops to match what my various balistic calcs say they should be based on velocity and bc I have to adjust velocity by well over 100 fps to get close. This is off an ohler so I am assuming its not that far off. Again that's all a starting point and you need to verify in the field and confirm dopes but in running a search I didn't find the level of detail I was looking for so wanted to see what are the most useful tips and tricks you guys have found fromo start to finish. Would you rather tweak BC which often isnt shown in a balistic calc but rather a hidden variable or tweak velocity to match things up? Or would you rather just get actual drops at a few yardges and tweak both till you get them to match up as closely as actual field drops. Any thoughts or details on your procedures from start to finish would be very helpful.
Thanks and all the best,
Don

 

[MMERSS]

Buy this DVD and watch it couple of times. Putting Rounds On Target With Bryan Litz

The DVD will explain how to prepare for and conduct calibration (confirming drop charts).

Drop charts can be a tail chasing experience without the necessary work completed beforehand. This DVD will discuss the steps necessary to complete before and during calibration.

 

[7magcreedmoor]

No matter how good the chronograph, if it is optical and close-spaced, there will be some error. It is very difficult to time precisely the movement from one point to another only a foot or two apart. I use three distances for trajectory validation. If the BC value is reliable (go to Bryan Litz for good BC numbers on most bullets sold today) adjusting the MV works well. If you don't get closely matching drops at both downrange targets, then maybe you want to fine-tune the BC a bit, but I find that Berger's BCs work well enough so that if I lean more heavily on the longest range drop data, the nearer distance will be "close" enough for my target sizes.

 

[FearNoWind]

Even in long range competition, where .5 MOA makes a very big difference, I rely on a method similar to what 7mgcreedmoor describes. But I'm not sure I do it exactly the same way. I run my basic dope chart using the best BC data I can find (if it isn't in Bryan Litz's book I may use it but only with some reservations) and visit the range. I'll shoot 200/300/450/500/600/800/900 and 1K (40 rounds) with sight adjustments suggested on the preliminary dope chart. Then compare the elevation of each shot on target with the dope sheet. I then calculate true trajectory values with those on the dope sheet, make necessary corrections.
Just for kicks I then run a line chart, using my computer spread sheet software, to parallel the curve of the preliminary dope sheet with actual field results. If those charts look odd and the slope of the curves are too dramatic I re-examine my data to find any error I might have made in its collection.

 

[4xforfun]

I just watch all them long range hunting shows on the TV. They say simply buy xyz scope, dial it up, and you are GTG!!!

 

[stomp442]

Nothing beats real world data. if you want to know what your dope is for a certain range go shoot that range and record your findings. Keep note of wind conditions elevation and temp. when making a drop chart for my rifles I go the the range and set up targets every 50 yards from 200 - 1000 and write down what it takes to hit center at that range.

 

[Canadian Bushman]

First find true barrel twist, bc, and MV.

Then with every batch of loaded rounds (50) i check mv and SD. I run these numbers in bergers barrel twist calculator in my average environment for aprx bc.

I use the avg bc and mv in shooter to predict drops and go shoot and record the results every 2-3 hundred yards out to 80% of my supersonic range.

This usually eats up 10-20 shells, but leaves me spot on for the remaining 30-40.

 

[CA48]

Ballistic Programs can be frustrating. For some cartridges I put in the advertised BC and chronoed velocity and they are dead on up to 1000 and past that point it takes a lot of tweaking. Most of the time I have have to put in ridiculous BC values and velocity numbers +or- 100 fps of my actual velocity. Create stepped bc profiles sometimes multiple stepped BC profiles for 1 cartridge to get things to match up. 1 profile from 0-800, another from 800-1000 and another from 1000-1200. Then it can vary past there. I am using Bullet Flight military ver. But would like to try CB 1.0 and applied ballistics. Before you start collecting any dope or trajectory validation always check your zero. And have your inputs as accurate as possible even if your zero was dead on yesterday check it today and make sure 1 click adj. is actually 1/4Moa and if not a lot of programs will let you calibrate for your adj. error. Record the conditions, use consistent form, shoulder to stock pressure, bi-pod load pressure. Recently on my cartridges with longer barrel life I just shoot and record dope every 10 to 50 yards depending on the distance, out to the max range I plan on shooting at and really get to know my rifle. You won't always have this luxery with over bore cartridges with short barrel life and that's when I really try to tweak my ballIstic program and shoot at several ranges then try to match it all up.

 

[Andy Backus]

We carry all of Bryan Litz' DVD's and books at the LRH Store - CLICK HERE.

 

[MMERSS]

Right on Andy,

Please edit my original reply to reflect the LRH DVD link.

 

[406precision]

Alot of people over complicate the issue. It is really as simple as garbage in equals garbage out. You need to put in the most precise measurements you can to get the most consistant results back. Determining bc and proving it is a complicated and tedious task.
Understanding how to properly enter and evaluate data in your ballistics program is paramount.
applied ballistics is one of the easiest and certainly accurate ones out there once you have all your info loaded hit the range try to shoot 200 to 1200 in what ever steps you prefer.
then run the ballistic calibration tool on the app and it should fine tune your info really well.
we have used these methods beyond 2000 yards with very good results.
alot of times shooter error can skew your inputs so take time to get quality rounds down range
remember chronographs lie more than politicians

 

[Andy Backus]

By the way, Bryan Litz has written that after extensive testing of many chronographs, he believes the MagnetoSpeed V3 is the most accurate chrono on the market today.

 

[Canadian Bushman]

By the way, Bryan Litz has written that after extensive testing of many chronographs, he believes the MagnetoSpeed V3 is the most accurate chrono on the market today.

Alot of my numbers started to jive after using the v3 to verify my velocities.