Quick Field Methods For Determining Density Altitude.

mxgsfmdpx

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We had an informative discussion going in one of @Ucsdryders threads and I wanted to move it to its own space.

@Formidilosus and @Marbles shared some good information and I’m wondering if you guys could generalize how you handle long range ballistics factoring in environmental conditions at different altitudes.

I’ve found that by the time somebody pulls out a kestrel or a phone and inputs all of their weather information etc, they have either lost sight of the animal, the yardage has changed on a moving target and they have to change their number, or they fumble around and never get a shot off.

I’m looking for real world tactics used to get proper environmental conditions when hunting and time is short. Meaning, you don’t have time or internet for a full real world current density altitude calculation.

I use an old, very basic line graph chart that I have laminated on a key ring. This line graph gives you a simple to follow “cheat sheet” for obtaining basic density altitude. On the same key ring are color coded laminated cards, sorted in order by temp. So red cards are 3,000 foot DA, orange cards are 5,000 foot DA, yellow cards are 7,000 foot DA etc. They are then in order from temp low to high with bold numbers to see elevation and wind corrections. This is small enough to fit in my pocket or bino harness and access instantly.

I make these cards up before going on a hunt with planned hunting elevations and known weather forecast. That way the key ring isn’t crazy with too many cards.

Is there a more effective way to manage this? I’ve been lucky to have good success with multiple long range kills per year using this method but I’d love to learn more.
 

Formidilosus

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We discussed DA and usage quite a bit in this thread-

 

Marbles

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For the sake of ths thread I will repeat it.

I look at a Kestrel before I need the data, then check it again if I think conditions have changed significantly.

Within my shooting range on animals, a for my 243, a 5000 ft DA error is less than 2.5 inch shift vertical (0.1 mil difference in dialing). So I have drops memorized for 3000 ft DA. I need to make cards for 0 ft DA and 6000 ft DA, but have not done so.

I suspect just adding or subtracting 0.1 mil past 300 yards will be adequate, but I need to make the cards to see.

Speaking of that, as I'm at home with a sick kid, I should probably stop reading Rokslide and get that done.
 
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mxgsfmdpx

mxgsfmdpx

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We discussed DA and usage quite a bit in this thread-

Nice I just read through that all. That’s excellent info. It seems like you are a fan of the old line graph cheat card for determining density altitude as well? Do you still utilize this or is there a better/quicker method these days?
 

SouthPaw

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I carry the DA line chart in my bino pouch for redundancy. But basically I do this (which I learned reading here):

Wake up, check Kestrel for DA and Temp while coffee is making. Plug DA and Temp into my App, screenshot chart, set to phone lock screen, then take 30 seconds to figure my correction for quick drops and gun wind #. Then I'm good to go hunting for the day without needing anything but range. If the temp or elevation swings a bunch during the day, I'll take a moment to check kestrel DA and repeat.
 

Formidilosus

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Nice I just read through that all. That’s excellent info. It seems like you are a fan of the old line graph cheat card for determining density altitude as well? Do you still utilize this or is there a better/quicker method these days?


A couple of key points to outline:

1). It takes about 2,000ft DA change to change .1 mil at 800 yards for most normal/common combinations.

2). Using just the DA chart, actual temp, and actual elevation; from -1,000 ft DA, to over 16,000 ft DA measured, the chart has never been off more than 200 feet.



In order of what I use-

1). RF bonus with ballistics. Inside of 600’ish yards, I’m using quick drop.

2). Data chart on phone lock Screen. I set the DA to what it should be on average where I will be hunting, then screenshot the chart and set it as my lock Screen on the phone. Any movement or any button press and the chart is visible.
In the mornings I check DA with a Kestrel, and as long as it is within 1,000ft DA of the chart, I don’t adjust it. If it is more than 1,000 ft DA off, I check at 800 yards and see what the error is- if it is .1 mil or less, I don’t change it. If it is .2 mil different, I screenshot a new chart. In the afternoons if it heats up dramatically I will check it again.

3). In especially long shots- 900’ish plus with time, I will input the current DA and get an actual elevation from the ballistic app.

4). As a back up, I have the DA chart on the gun, and data cards for 2,500ft, 5,000ft, 7,500ft, and 10,000ft on the gun as well, and will choose whichever is closer to actual DA.
 
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mxgsfmdpx

mxgsfmdpx

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I carry the DA line chart in my bino pouch for redundancy. But basically I do this (which I learned reading here):

Wake up, check Kestrel for DA and Temp while coffee is making. Plug DA and Temp into my App, screenshot chart, set to phone lock screen, then take 30 seconds to figure my correction for quick drops and gun wind #. Then I'm good to go hunting for the day without needing anything but range. If the temp or elevation swings a bunch during the day, I'll take a moment to check kestrel DA and repeat.
That’s amazing that folks are using that same old line chart I’ve been using for so long haha.

This is a good tactic I saw this posted in the thread that @Formidilosus linked. Great info in there!
 
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mxgsfmdpx

mxgsfmdpx

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A couple of key points to outline:

1). It takes about 2,000ft DA change to change .1 mil at 800 yards for most normal/common combinations.

2). Using just the DA chart, actual temp, and actual elevation; from -1,000 ft DA, to over 16,000 ft DA measured, the chart has never been off more than 200 feet.



In order of what I use-

1). RF bonus with ballistics. Inside of 600’ish yards, I’m using quick drop.

2). Data chart on phone lock Screen. I set the DA to what it should be on average where I will be hunting, then screenshot the chart and set it as my lock Screen on the phone. Any movement or any button press and the chart is visible.
In the mornings I check DA with a Kestrel, and as long as it is within 1,000ft DA of the chart, I don’t adjust it. If it is more than 1,000 ft DA off, I check at 800 yards and see what the error is- if it is .1 mil or less, I don’t change it. If it is .2 mil different, I screenshot a new chart. In the afternoons if it heats up dramatically I will check it again.

3). In especially long shots- 900’ish plus with time, I will input the current DA and get an actual elevation from the ballistic app.

4). As a back up, I have the DA chart on the gun, and data cards for 2,500ft, 5,000ft, 7,500ft, and 10,000ft on the gun as well, and will choose whichever is closer to actual DA.
RF binos with ballistics would save me an extra step for sure. Are the Revics the go to?

Phone Lock Screen is a great idea we used to use that when running and gunning coyotes from side by sides and ATVs. I don’t normally carry my phone in a pocket when hunting. Going to this and adjusting numbers when needed would be handy. Faster than flipping through my cards for sure.

For really long shots like cow elk with potential time I still like to use Strelok Pro when I can as it lets me use DA input, and has been really accurate in what I’ve seen. Multiple 1,000 plus yard big game kills using that app.

Appreciate the ideas!
 

Marbles

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Another thing, wind number changes with DA, at 0 and 3000 ft DA 5 mph is the closest whole number for wind. At 6000 DA 6 mph is the best fit.
 

Formidilosus

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So @Formidilosus fair to say that using the Revic RF Bino's, then you just trust the dial up (assuming that you have the correct profile selected)? (e.g., it takes all the environmentals, except wind (I have to input that), into its algorithm)

Correct. The only real thing I watch for is that the binos are acclimatized to the actual ambient temp. So in cold weather it is left outside at night, the bino oouch is outside any clothing, and the lid is open when glassing if possible. In hot weather, make sure the bino isn’t laying out or getting heated up by the sun.
 

Marshfly

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I normally pull the kestrel out every couple of hours, sync it with my iPhone ballistic app, then compare that to my normalized dope chart on the objective housing on my scope. If you choose the settings for the dope chart you make available well, as in "average" temp and elevation, it will be very close.
Or at least it has been for me and most of the places I hunt in Montana.
 

Marbles

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In creating my dope chart, for a 108 ELDM at 2780 fps out to 450 yards 3000 ft DA is more than good enough for 0 ft DA to 6000 ft DA. Past 450 yards, out to 600 yards (as far as my chart goes) the variance from 3000 ft DA is effectively -0.1 mil for 0 ft DA and +0.1 mil for 6000 ft DA.
 
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mxgsfmdpx

mxgsfmdpx

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In creating my dope chart, for a 108 ELDM at 2780 fps out to 450 yards 3000 ft DA is more than good enough for 0 ft DA to 6000 ft DA. Past 450 yards, out to 600 yards (as far as my chart goes) the variance from 3000 ft DA is effectively -0.1 mil for 0 ft DA and +0.1 mil for 6000 ft DA.
I ran a bunch of numbers in two different calculators for my .223 shooting 77 TMKs for expected/potential DA swings while hunting moose in AK in 3 weeks.

Unless the weather gets totally crazy I found that at a 500 yard maximum I won’t see more than +/- 0.1 MIL discrepancy and won’t go below 1,815 impact velocity. Quick chart is ready to roll.
 
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I keep it pretty simple. It’s easy to grab elevations of the area you’ll hunt prior to getting there. I calculate everything for 32° for my hunt spots. This gives me wiggle room for the really cold days and the days that are a bit warmer. I usually hunt in the same areas, so I know what the weather usually does and the change in elevation in the area…never changes. The variance isn’t more than 2000’ vertical.

I do have an antelope hunt I drew this year that’s in a new area to me. I’ll do some e-scouting and grab an average elevation. Since it’s a warmer time of the year to hunt, I’ll likely use 40° as my average temperature.

In the past, I’ve leaned on the ballistics app, but I find that it’s a really slow process. This year I’m going to toy with a taped and marked turret (poor man’s custom turret), quick drop, and a chart taped on top of my scope. A bit of memorization mixed in, and I should have much faster shooting solutions.

I do carry a kestrel but rarely use it. More than DA, I have it for the really windy days when the wind is difficult to judge.
 
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