Different Dope Cards for different Altitude/DA

[SuperBoot]

Hey fellas,

I was wondering if someone here that uses printed dope cards could give insight on how much you can get away with when you're using a card that was made for a specific DA/temperature/humidity, etc.
I primarily use a kestrel at matches, but I really need to start carrying backup data in case shit happens.

For example, if I had a card I made for a DA of 5800, at 60 deg F, and 30% Humidity, how much use could I get out of that card before having to change to a different one as a result of environmental change? Is there any variable that's more important than the other, or one that you use as a benchmark when you use different cards? (i.e. different cards for every 20 deg F, or different cards for every 1000ft DA)

Thanks in advance

 

[Jack Master]

Have a read and study here.

How do you have a paper chart for Density Altitude (DA) changes in your dope? Do any of you have a DA sheet in your Data Book?

I have read and been told to have drop charts for every 2000DA change. My home range is usually around 2000DA. This means I need a drop chart for -2000ft, 0ft, 2000ft, 4000ft, 6000ft, 8000ft, 10,000ft. That's 7 pages in a dope book for one rifle. I don't really want to have that many pages for one rifle (yes, I want ONE data Book for all my rifles). With 3 rifles is 21 pages to sift through. So... below is the chart I made for changing DA. Now I have 2 pages, my Home range dope chart with the wind information on the back and a DA dope chart.

Things to Note

1. Data recorded - at the top of the chart is how I got the DA numbers. This way I can reference how temperature might change the DA as well as the station pressure. (note the comment in the margin about how temp change = DA change)
2. All of these are at 50% humidity. To keep this simple I had to eliminate a variable, humidity was it. While I think it will effect things more after 1000yds I don't think it has enough variance inside 1000 to worry about.
3. Wind - The wind row has 2 numbers in it. The 2 numbers are the wind speeds that are equivalent to the wind hold for 2000DA. Example - if I'm shooting at 6000DA, 800 yards - a 7mph hold is 0.9 mils (6mph from 2000DA) and a 12mph hold is 1.6mil (10mph hold for 2000DA) this allowed the chart to re-use 2 columns of information for each DA change and for me to know what my Rifle MPH is at each DA.
4. After doing this I think the chart will work out to 1000 or 1100 yards. After that a more refined DA chart may be warranted. At 1100 yards jumping 2000DA is a 0.4 mil jump, that's about 16" of change. For an accurate shot I recommend consulting your Ballistic program on the longer shots with changing DA, but these values will at least give you a starting point if you don't have any other information. of you'll need to pin down your true DA and guess between numbers if needed.
5. I presented this chart in 2 ways. 1st - straight data. 2nd is the plus or minus from the home range value. Doing the 2nd version can help us understand how much DA can really effect our dope. The 2nd if more for informational used and not necessarily something I would have in my data book.

Let me know what you think.

1st chart Raw DA values
View attachment 7172626

2nd chart - Difference in DA from my home range.
View attachment 7172627

 

[Steel head]

I run two cards each for my 260 and 7 saum.
One for 1500 DA at 45 degrees and one for 4000 at 75

I use my app to fill in the gaps if needed.

 

[SuperBoot]

Have a read and study here.

Thanks man.

I'll probably make a few sets for different DA with set temp and humidity.
Do you have a few different cards for different environmentals at your home range? Lots of places I shoot here could be 20 deg/50% humidity in the morning, and 55 deg/20% humidity at noon. Is the change notable enough to warrant a different set of come ups?

Does anyone have an Excel template ready to go that they've used in the past?

 

[Jack Master]

Thanks man.

I'll probably make a few sets for different DA with set temp and humidity.
Do you have a few different cards for different environmentals at your home range? Lots of places I shoot here could be 20 deg/50% humidity in the morning, and 55 deg/20% humidity at noon. Is the change notable enough to warrant a different set of come ups?

Does anyone have an Excel template ready to go that they've used in the past?

1. Look at the charts in that post I sent you. Go to that page and you'll see them. That is a dope card with 7 different DAs.
2. Forget about humidity. Set it to 50% and leave it. 0% to 100% change will be about 3 inch change at 1000 yds.
3. A 15 degree change is about 1000 feet of DA change. I round to the nearest 2000 DA for inside 800 yards. If you are shooting more than that 30 degrees might start to matter.
4. My home range is 0 DA in winter. 1000 DA in spring and fall and 2000DA in the heat of the summer.

 

[Coyote-6]

I’m still finding my legs with serious LR shooting, but I have an unhealthy (although very different) relationship with DA coming from the aviation world. I would think that having dopes for DA ranges as your use criteria should be sufficient to not have to deal with temp, humidity, or altitude. Each of these components (humidity is a very small part as noted above) are part of the DA equation already, so changes in those would change the DA. Further, as far as basic aerodynamics are concerned, the reason we care about any of these individual components is because of their effect on air density (ie. lower temp = denser air = more drop).

Pressure Altitude (PA) = (29.92 - current pressure setting) x 1,000 + field elevation

DA = PA + [120 x (OAT - ISA Temp)]

To correct for 50% humidity (not really all that necessary) add the following to DA:
@SL = +16%, @3000ft = 7%, @5000ft = 5.5%


OAT: Outside Air Temp
ISA Temp: Standard temp at sea level (15*c) then corrected for your altitude by subtracting 2*c for every 1000 ft in altitude) For me in OH, being roughly 1000 ft MSL, I use 13*c)

Disclaimer: This is using fluid dynamics and meteorological knowledge from the aviation mindset. I’m not experienced enough in advanced ballistics to know if other factors make my point useless or outright wrong!


Long post, almost done! If my logic holds up here, I plan on creating dope cards in 500ft DA increments and picking one for each time I go out. Ohio DA’s only fluctuate between -800 to 3000 annually.

 

[_Windrider_]

1. Look at the charts in that post I sent you. Go to that page and you'll see them. That is a dope card with 7 different DAs.
2. Forget about humidity. Set it to 50% and leave it. 0% to 100% change will be about 3 inch change at 1000 yds.
3. A 30 degree change is about 1000 feet of DA change. I round to the nearest 2000 DA for inside 800 yards. If you are shooting more than that 30 degrees might start to matter.
4. My home range is 0 DA in winter. 1000 DA in spring and fall and 2000DA in the heat of the summer.


View attachment 7215558
View attachment 7215559

30 degrees is a 2000 foot change.

 

[_Windrider_]

I’m still finding my legs with serious LR shooting, but I have an unhealthy (although very different) relationship with DA coming from the aviation world. I would think that having dopes for DA ranges as your use criteria should be sufficient to not have to deal with temp, humidity, or altitude. Each of these components (humidity is a very small part as noted above) are part of the DA equation already, so changes in those would change the DA. Further, as far as basic aerodynamics are concerned, the reason we care about any of these individual components is because of their effect on air density (ie. lower temp = denser air = more drop).

Pressure Altitude (PA) = (29.92 - current pressure setting) x 1,000 + field elevation

DA = PA + [120 x (OAT - ISA Temp)]

To correct for 50% humidity (not really all that necessary) add the following to DA:
@SL = +16%, @3000ft = 7%, @5000ft = 5.5%


OAT: Outside Air Temp
ISA Temp: Standard temp at sea level (15*c) then corrected for your altitude by subtracting 2*c for every 1000 ft in altitude) For me in OH, being roughly 1000 ft MSL, I use 13*c)

Disclaimer: This is using fluid dynamics and meteorological knowledge from the aviation mindset. I’m not experienced enough in advanced ballistics to know if other factors make my point useless or outright wrong!


Long post, almost done! If my logic holds up here, I plan on creating dope cards in 500ft DA increments and picking one for each time I go out. Ohio DA’s only fluctuate between -800 to 3000 annually.

The problem with using DA is this, a given DA can be comprised in multiple different ways with different pressures temps and humidity. Saying 4000 DA (26.92 in and 63 degrees) is no different than 4000 DA (29.92 in and 120 degrees) Is wrong.
both are 4000ish DA, but do you think the trajectory is the same?

in aviation you can assume it’s the same because the engine only cares where it is not how it got there. In a bullet, temp changes velocity. The velocity at 63 is slower than 120 so how can you say just having a 4000 ft da card will suffice?

 

[DellaDog]

... both are 4000ish DA, but do you think the trajectory is the same?

Actually, yeah, that’s what I always thought.

 

[_Windrider_]

Actually, yeah, that’s what I always thought.

Different temps usually equal different velocity which equals different trajectory

 

[Coyote-6]

Different temps usually equal different velocity which equals different trajectory

Because different temps change air density, nothing else. I challenge someone to run it through a ballistics program to change altitude and temp to maintain the same DA and I’d be shocked if your mils change. Unless it affects propellant performance, the external ballistics don’t change. A bullet doesn’t care if it’s 200*f or -tp*f, it only cares about the fluid it has to move through, density.

edit: cartridge temp does matter (how much out to 1000m is debatable), which would affect trajectory by increasing velocity, but I think we can omit that from this discussion since you probably don’t have different dopes for 10 rounds and 100 rounds.

 

[_Windrider_]

Because different temps change air density, nothing else. I challenge someone to run it through a ballistics program to change altitude and temp to maintain the same DA and I’d be shocked if your mils change. Unless it affects propellant performance, the external ballistics don’t change. A bullet doesn’t care if it’s 200*f or -tp*f, it only cares about the fluid it has to move through, density.

Velocity changes due to temp. The higher the temps the faster the bullet.

Edit to add this is a general rule. Powders are becoming more and more temp stable so it’s possible it’s less of a factor depending on your recipe.

also, hard to beat that challenge without changing the velocity as well. Most calculators require you to input that velocity. Again if you measured your velocity at 52 degrees and it’s now 105 degrees, is it the same or faster?

 

[Coyote-6]

Velocity changes due to temp. The higher the temps the faster the bullet.

Edit to add this is a general rule. Powders are becoming more and more temp stable so it’s possible it’s less of a factor depending on your recipe.

also, hard to beat that challenge without changing the velocity as well. Most calculators require you to input that velocity. Again if you measured your velocity at 52 degrees and it’s now 105 degrees, is it the same or faster?

100% dependent on powder temp stability. To that end, you’re right. But I wonder just how much affect that has. To test, one would need to chrono cold bore on a nice cold day and then heat another round and see how trajectory is affected in the same DA.

As noted in my disclaimer earlier, I’m unsure how temps really affect muzzle velocity due to powder burn rates

 

[Coyote-6]

Found this for IMA powder:

"For the IMR powders, each change of temperature of one degree Farenheit changes the muzzle velocity by 1.7 fps in the same direction. Thus, and increase in the temperature of the powder amounting to 20 Farenheit could be expected to increase theMV by 34 fps."

@TacticalDillhole , using these numbers, could you do a comparison for 10*f and 100*f? This is what I would consider worst case extreme spread for a given location.
1. Only change muzzle velocity and leave the rest the same,l.
2. Change temp and altitudes, making sure to keep DA the exact same, along with changing the MV with the same as #1 above. Then compare.

 

[_Windrider_]

Found this for IMA powder:

"For the IMR powders, each change of temperature of one degree Farenheit changes the muzzle velocity by 1.7 fps in the same direction. Thus, and increase in the temperature of the powder amounting to 20 Farenheit could be expected to increase theMV by 34 fps."

@TacticalDillhole , using these numbers, could you do a comparison for 10*f and 100*f? This is what I would consider worst case extreme spread for a given location.
1. Only change muzzle velocity and leave the rest the same,l.
2. Change temp and altitudes, making sure to keep DA the exact same, along with changing the MV with the same as #1 above. Then compare.

I deleted my post as it wasn’t right. This will have to wait till i get home and i can use my laptop and use AB Analytics or coldbore. It’s too hard on my phone or iPad. Butt changing the velocity 153 FPS resulted in a mil difference in drop in the same DA.

 

[Coyote-6]

Interesting. In going down the rabbit hole, there’s a big difference between powders in TSC (Temperature sensitivity coefficient) which does impact drops. However it’s generally seen in seasons (winter vs summer) so not really smaller 30-40*f temp swings you could see in a day. It makes me wonder, can you simply re-zero every once in awhile to fully compensate for change in seasons? Then cartridge temp is already solved in the zero, so we are left with ambient temp affecting bullet in flight given a same-DA situation.

 

[Deleted member 113831]

Run 5 trajectories for 0, 2k, 4k, 6k, 8k ft elevation @ 60 degrees.

Separate chart... average 20 degree temp change per yard line from 600 on out. Factoring in difference in velocity due to powder burn and change in DA together.

0-500, any likely temp or alt change amounts pretty close to fuck all...

This will get you to within a .1 or .2 of actual all the way to 1200 or so. Don't make this shit harder than it has to be.

 

[Coyote-6]

Run 5 trajectories for 0, 2k, 4k, 6k, 8k ft elevation @ 60 degrees.

Separate chart... average 20 degree temp change per yard line from 600 on out. Factoring in difference in velocity due to powder burn and change in DA together.

0-500, any likely temp or alt change amounts pretty close to fuck all...

This will get you to within a .1 or .2 of actual all the way to 1200 or so. Don't make this shit harder than it has to be.

+1. Think this is the way to go. Long story short; DA can get you close enough for 600-800yds, but doesn’t take drop from TSC.

this was fun!

 

[_Windrider_]

It’s all academic. Just discussing. Most techniques will get you within.1 or .2

 

[Coyote-6]

It’s all academic. Just discussing. Most techniques will get you within.1 or .2

Agreed, and I really enjoyed the thought exercise and challenge from you. Really, I don’t get that much anymore.

Besides, in any of the theoretical situations, I still missed because I miscalculated the wind...

 

[_Windrider_]

Agreed, and I really enjoyed the thought exercise and challenge from you. Really, I don’t get that much anymore.

Besides, in any of the theoretical situations, I still missed because I miscalculated the wind...

No you added too much spin drift

 

[Jack Master]

Fellas.
I did this exercise to make the sheets above. And, this is why i made sure to list what temp I did the DA calculation with. In the right hand margin of each sheet it says " for each +-15 degrees change +- 500 DA". I will manually add this DA adjustment to my field DA to account for the powder burn change. I got this 500DA from lindy's website and checked it myself to verify it. Hornady 4dof takes the powder temp stability into account, this is where I checked it for H4350.

If I did this chart again I would use 60 degrees as my base line. 1. It is closer to the standard temp. 2. Its closer to the middle range of my shooting (20 deg to 100 deg).

At 500DA per 15 degrees.

 

[Coyote-6]

Fellas.
I did this exercise to make the sheets above. And, this is why i made sure to list what temp I did the DA calculation with. In the right hand margin of each sheet it says " for each +-15 degrees change +- 500 DA". I will manually add this DA adjustment to my field DA to account for the powder burn change. I got this 500DA from lindy's website and checked it myself to verify it. Hornady 4dof takes the powder temp stability into account, this is where I checked it for H4350.

If I did this chart again I would use 60 degrees as my base line. 1. It is closer to the standard temp. 2. Its closer to the middle range of my shooting (20 deg to 100 deg).

At 500DA per 15 degrees.

I’m confused as to what has changed between the 2 pages. Take the -2000DA for example; temp is the same, pressure is the same. And the 0DA is identical between the 2.

 

[Jack Master]

I’m confused as to what has changed between the 2 pages. Take the -2000DA for example; temp is the same, pressure is the same. And the 0DA is identical between the 2.

Each sheet has the same data for the same rifle (same DA, same temp, same pressure). The 1st sheet is the actual dope. The 2nd sheet shows how much change there is from the 2000 DA. I showed this so we can study or understand how much the DA is effecting out trajectory.

 

[Deleted member 113831]

Just went back and looked at the numbers again.

Given: 6.5 Creed with a powder burn rate adjustment of 0.5fps per degree ambient.

Basically, set up those 5 base line trajectories at 0, 2000, 4000, 6000, 8000 ft. altitude at 60 degrees F.

From 20 degrees to 100 degrees using any of those baselines, you only need .1mil adjustment per 40 degrees temp difference, and only then once you get to 800+ yards.

 

[SuperBoot]

Run 5 trajectories for 0, 2k, 4k, 6k, 8k ft elevation @ 60 degrees.

Separate chart... average 20 degree temp change per yard line from 600 on out. Factoring in difference in velocity due to powder burn and change in DA together.

0-500, any likely temp or alt change amounts pretty close to fuck all...

This will get you to within a .1 or .2 of actual all the way to 1200 or so. Don't make this shit harder than it has to be.

thanks dude, that’s what I was looking for. I was more or less trying to have data I could run out of my pocket in a pinch should my electronics shit the bed. Local matches here rarely go past 1100 or so.

Again, does anyone have an excel template they’ve used and want to share so I can bear the fruits of your labor? lol.

 

[AR10ShooterinNC]

Are you looking for something like this:

 

[SuperBoot]

Are you looking for something like this:

Not sure if you tried to attach something but it didn't show up.

 

[AR10ShooterinNC]

Not sure if you tried to attach something but it didn't show up.

Yes, let me try a different way .

 

[SuperBoot]

Yes, let me try a different way .View attachment 7217298

Awesome, yep, that looks great. Don't know if you can attach files here, but I'd appreciate it if you could send me that in a file I can edit myself. Maybe PM or email?

 

[_Windrider_]

Yes, let me try a different way .View attachment 7217298

Lookin a little Tiborasaurus Rexy

 

[AR10ShooterinNC]

Lookin a little Tiborasaurus Rexy

Not sure where I got them from, but they work for me.

 

[Millerman2004]

Hey fellas,

I was wondering if someone here that uses printed dope cards could give insight on how much you can get away with when you're using a card that was made for a specific DA/temperature/humidity, etc.
I primarily use a kestrel at matches, but I really need to start carrying backup data in case shit happens.

For example, if I had a card I made for a DA of 5800, at 60 deg F, and 30% Humidity, how much use could I get out of that card before having to change to a different one as a result of environmental change? Is there any variable that's more important than the other, or one that you use as a benchmark when you use different cards? (i.e. different cards for every 20 deg F, or different cards for every 1000ft DA)

Thanks in advance

Doing the math for your cards directly will teach you the scale of differences and what variables affect things the most, etc. I recommend diving into the manual production of cards either by BARO inch increments or by DA. If you created the cards yourself, you'll tend to recall ballpark figures and guesses will be more like educated guesses.