Ballistic DOPE Question

Downeast

Happy to be here
Benefactor
Joined
Feb 10, 2017
Messages
3,359
Location
28433
Rating - 100%
3   0   0
Since it's been raining for the last week or so I started looking over my "dope" for the last 4 years shooting one of my rifles. I have been recording weather as well as "come-ups" everytime I shoot the rifle (25 days on the range with this rifle) over the last 4 years. Round count is about 800. I rotate rifles everytime I go. I start with Strelok and that usually gets me on the steel and then I adjust to hit as close to center as possible. I record all data for that shooting period. I haven't changed loads except to replace bullets and powder as needed. Things are ok out to 400 yards but as I go out to 800 things start to get screwy. Wind is not a factor since I only shoot on calm days. Could temperature change POI this much at longer ranges? I have the data, I just haven't looked at it. I started with elevation as needed to hit the target. It's a bit confusing but for example at 600 yards I dialed up 3.4 mils (200 yard zero) to hit center on 3 different days. Then, on three other days I dialed up 3.2 mils to hit center. Then, on 3 other days I had to dial 3.8 to hit center. I guess that is why they have "sighters" before matches? It's kind of tough to make a dope card when you have this much variation at long range.


6.5 Creed with 140 grain Berger VLD. Actually data in MILS.
This is not data generated from Strelok or other apps.
Values are for specific days with hits on target. 200 yard zero.
 

Attachments

  • 6.5 Creed Ballistic Data.pdf
    60.3 KB · Views: 3
Last edited:
Temperature, barometric pressure, humidity can all effect your hits at longer ranges.
Everything has an effect on your bullets and it shows up more the father it gets from the barrel.
 
I failed to mention that these numbers were not consecutive days. I sorted them when I probably shouldn't have.

I am beginning to realize that. What I may do is go back and dig up the temps, BP and humidity and see just how much of an impact they have. It's quite an eye opener to see it in a table. Almost 1/2 mil at times. That's a lot at 800!
I would assume that temperature has the biggest impact, followed by humidity and BP.
 
Actual density altitude is the important number. It is what changes your bullet dope and is combination of real altitude, barometric pressure, humidity and temp. Powder temp effects on most modern powders are pretty small. Extremes can cause issues but normal ranges will not have a huge impact.
 
Most good ballistocs apps allow you to add density altitude directly. Kestrels and phones can supply the info. Several apps for phones as well.
 
Actual density altitude is the important number. It is what changes your bullet dope and is combination of real altitude, barometric pressure, humidity and temp. Powder temp effects on most modern powders are pretty small. Extremes can cause issues but normal ranges will not have a huge impact.

I used the density altitude function on Strelok to get me on target. Then I dialed to get the center of the target. On some days the POI (center) was 3.2 mils, on others it was 3.4 or even 3.8.

Oh, with Strelok the data did not deviate more than 0.1 or 0.2 mils on a given date for a specific range. But the POI may have been off by 6 inches. I then had to dial to get on bullseye for a group.

Fun stuff! I guess what I'm asking if for those of you who have been shooting LR a long time does your dope (elevation) settings for certain ranges change everytime you go out? And if so, by how much?
 
Last edited:
I used the density altitude function on Strelok to get me on target. Then I dialed to get the center of the target. On some days the POI (center) was 3.2 mils, on others it was 3.4 or even 3.8.

Not unexpected. Two solutions. One is 2900 and the other is 1900 for density altitude. Which one is which?

Screenshot_20200806-151136_Applied Ballistics.jpg Screenshot_20200806-150939_Applied Ballistics.jpg
 
Also did you true up you data? You usually want to true your dope at a range close to transonic. The gun above i got dope based on 100 yard zero and labradar. Then I shot at 1100 yards with the predicted data and adjusted to get good hits. Then put that number back into the app as a correction to correct all the data between 100 and 1100. Then confirmed that data between 100 and 1100.
 
Last edited:
OK, Thank you TSC. I learned something today. :cool:

Strelok Pro allows for those corrections I believe (velocity?)
 
So at 600yds each .1mil is an adjustment of 2.16"

You stated the range of adjustment is 3.2 to 3.8 MIL a variance of .6 MIL or 12.96 inches.

I can guarantee you half of the 12.96" of "play" is improper parallax in the optic. So that moves you to 6.48" of adjustment or .3 MIL of variance.

.3 MIL of variance is easily accounted for a 50-100FPS ammunition flux from winter to summer time.

So Great job on keeping data, I would work on your ability to tighten up your parallax setting and see if you can cut that .6 MIL error in half.
 
Last edited:
OK, Thank you TSC. I learned something today. :cool:

Strelok Pro allows for those corrections I believe (velocity?)


Yes it does. You put your yardage and actual shot dope into it and it adjust velocity to correct for it.

Also little things start to add up. If you are not using an ap like applied ballistics and getting your latitude and azimuth to target to account for drifts then that adds in as well. It all adds up.

Getting good true dope with accurate density altitude and then using current density altitude to correct it for given conditions is the best starting point.

Also what twist barrel you running. It could also be you are only marginally stabile based on bullet rpm. There are calculators for that as well. Hot weather it will have a smaller effect where cold weather and a slower rpm or a barrel with tl slow of a twist for the bullet can cause bigger groups.
 
Last edited:
Also put it on paper at distance to get actual groups. At 800 yards a typical precision rifle is going to be about a 4 in group maybe larger depending on the shooter. Honestly I would start there and see what your group size is. Even at 1 moa it is 8 in which is not a horrible group but that accounts for most of you difference you might be seeing.

Steel lies...
 
Last edited:
So at 600yds each .1mil is an adjustment of 2.16"

You stated the range of adjustment is 3.2 to 3.8 MIL a variance of .6 MIL or 12.96 inches.

I can guarantee you half of the 12.96" of "play" is improper parallax in the optic. So that moves you to 6.48" of adjustment or .3 MIL of variance.

.3 MIL of variance is easily accounted for a 50-100FPS ammunition flux from winter to summer time.

So Great job on keeping data, I would work on your ability to tighten up your parallax setting and see if you can cut that .6 MIL error in half.

How could parallax cause issues at 600 yds? Most scopes are at the infinite adjustment at that distance?

Asking for a friend.:)
 
How could parallax cause issues at 600 yds? Most scopes are at the infinite adjustment at that distance?

Asking for a friend.:)
You would think but are not at infinite at all.

Uncorrect Parallax past 300yds is a error of 1 MOA as a base rule.

The more you dial, the worst it can get
 
Last edited:
You would think but are not at infinite at all.

Uncorrect Parallax past 300yds is a error of 1 MOA as a base rule.

The more you dial, the worst it can get

At 600 my vortexs are all at max or damn close to it, at 800 they are definitely maxed at the infinite setting. But then again I true them up at 1200 so paralax is a non issue at that range or at least it is limited by the scope and truing fixes it.
 
Last edited:
I have 3 inch black numbered stencils on a white background at set ranges that I use to correct for parallax. On this rifle I'm shooting a NF 12-42 X 56 scope. I also have a level on the scope. 28" Krieger barrel 1:8 twist.
I shoot steel to get things right (adjusting like above) and then switch to an adjacent paper target for "score". I'm using 18 inch shoot-n-c targets on top of standard F-Class 300, 600, and 1,000 yard paper targets. Bullseye are right at 1 MOA, X ring is approx. 1/2 MOA. I usually shoot 10 rounds either prone or off the bench in 15 minutes. Gotta hit that "X". A 3 inch "X" at 600 yards is quite challenging. The 6" bull is doable, but it's those "X"s that get me. :)

Thank you all for the comments and info.
 
Last edited:
So ignoring the point of impact if you shoot at the same point of aim what is you 10 shot group size? A decent precision rifle should do 1/2 moa. If it is larger than that then you need to fix that prior to worrying about dope.

If the wind is not steady the vertical spread should still be better than 1/2 moa even if the horizontal spread is bigger due to wind. So ignore wind correction for that exercise.
 
Last edited:
So at 600yds each .1mil is an adjustment of 2.16"

You stated the range of adjustment is 3.2 to 3.8 MIL a variance of .6 MIL or 12.96 inches.

I can guarantee you half of the 12.96" of "play" is improper parallax in the optic. So that moves you to 6.48" of adjustment or .3 MIL of variance.

.3 MIL of variance is easily accounted for a 50-100FPS ammunition flux from winter to summer time.

So Great job on keeping data, I would work on your ability to tighten up your parallax setting and see if you can cut that .6 MIL error in half.
Totally agree, there’s lots of errors in any scope that show up as the distance increases. There are some open sight shooters that can shoot better scores as such and even use the irons on any sight matches. Centering your eye to the ocular is good as well as placing the head angle giving the eye the same entry of light/image also helps. Consistency on ever aspect is one of the keys to accuracy, good luck.
 
Last edited:
So ignoring the point of impact if you shoot at the same point of aim what is you 10 shot group size? A decent precision rifle should do 1/2 moa. If it is larger than that then you need to fix that prior to worrying about dope.

If the wind is not steady the vertical spread should still be better than 1/2 moa even if the horizontal spread is bigger due to wind. So ignore wind correction for that exercise.
I'm shooting 1 moa overall and sometimes a little better at 600. I can usually get 3 or 4 "X"s at 600 on a "good day". Perfect score would be 100 10X. I'm usually in high 90's with some "X"s (1/2 MOA). Now I know why they have "sighters".
 
I’ll throw another source that gave me fits in elevation changes, that being a little branch that flowed parallel to the target line. Depending on the time of day the atmosphere density was changing enough to give a varying barrier to the bullets flight a good MOA. After catching on to the branch’s effects it taught me to always look for physical changes as did it rain the night before or even the height of the grass. All things matter.
 
Back
Top Bottom