Range Report Ballistic Card with Density Altitude

[Slope]

New to the forum, glad to have found it and hope to learn a few things to improve my long range shooting.

I will start with the question concerning using DA with ballistic cards.

Most of my shooting has been just out to 600 yards, and I am wanting to start getting out to 1000. Since my range has been limited to 600 I have just made up my own ballistics cards using my location and never really worried too much about taking into account humidity, pressure, and temp. I have recorded my zero summaries for temp change but that is about it.

My question is:How do I used a simple density altitude chart with my current ballistic cards. Do I need to make a new cards at say 500 ft elevations and then use the DA to adjust for my altitude and temp?

For instance, if I use a chart like what the FDAC has on it and determine that at 2000ft with a temp of 80 deg F that my DA is really 3500 ft. Now would I just turn to the card that I made at 3500ft and use it for my adjustment?

Could I also use the tables from Manual Calculation of Density Altitude to essentially get a slightly more accurate DA and again use it with a range card for the corrected DA? 29.92-(2000/1000) = 27.92 or a pressure altitude of 1824 which used on the DA chart at 80 deg F gives around 3750ft

Or does the ballistic card need to have the DA factored into it to work?

Basically I am trying to get away without having to use electronic software at the range. I could use one of the programs on my tablet, but I would rather use cards and charts that do not need batteries.

I really appreciate you help.

Thanks,
Slope

 

[Wildboarem]

I would assume you could have multiple cards for different DAs. Or 1 card with multiple DAs. Jbm ballistics has an option to make cards with different temps etc. Since DA can be closely related to temp at a given altitude you can just have a " temp " card. I would set it up so you have your intervals dependent in target size. Play with different DA numbers and you'll see what I mean.

 

[Cossack]

I would set up a card for 1 inch of pressure and different temperature. So say 30 in/hG and temp from 0 to 100F.
Here is how I got my cards going.
https://docs.google.com/spreadsheet...tZFdfWUl5NjF6Y1R0bHUybFE&usp=drive_web#gid=15

 

[Redmanss]

New to the forum, glad to have found it and hope to learn a few things to improve my long range shooting.

I will start with the question concerning using DA with ballistic cards.

Most of my shooting has been just out to 600 yards, and I am wanting to start getting out to 1000. Since my range has been limited to 600 I have just made up my own ballistics cards using my location and never really worried too much about taking into account humidity, pressure, and temp. I have recorded my zero summaries for temp change but that is about it.

My question is:How do I used a simple density altitude chart with my current ballistic cards. Do I need to make a new cards at say 500 ft elevations and then use the DA to adjust for my altitude and temp?
If it gives you a warm and fuzzy, sure, but most do it in 1k increments and cut the difference if in between.

For instance, if I use a chart like what the FDAC has on it and determine that at 2000ft with a temp of 80 deg F that my DA is really 3500 ft. Now would I just turn to the card that I made at 3500ft and use it for my adjustment?
Exactly.

Could I also use the tables from Manual Calculation of Density Altitude to essentially get a slightly more accurate DA and again use it with a range card for the corrected DA? 29.92-(2000/1000) = 27.92 or a pressure altitude of 1824 which used on the DA chart at 80 deg F gives around 3750ft
You're still ball-parking your figures unless you have something giving you the station pressure. The additional effort and math would not pay off enough in gained accuracy, instead giving you more chance of error.

Or does the ballistic card need to have the DA factored into it to work?
That's what we're talking about, right? Ballistics charts need DA factored in to be accurate.

Basically I am trying to get away without having to use electronic software at the range. I could use one of the programs on my tablet, but I would rather use cards and charts that do not need batteries.
Very understandable and easily done, so long as you put the preparatory work into it.

I really appreciate you help.

Thanks,
Slope

The easiest way(s) to ensure accuracy is to use something that does require batteries. Even if that is a Casio Pathfinder to give you station pressure, or the easiest is to have a Kestrel (which also gives you accurate wind readings), I recommend using at least one of the above. Yes, you can use a FDAC or Adaptive Consulting Quick Cards Adaptive Quick Card (AQC) to do the same all in one package, but it's not going to be as accurate when you start hitting the distance fringes. Inside 800yds on >2moa targets, no big deal, but once you start stretching it past there you will notice the difference and start experiencing more errors.

Key to all this is knowledge of your muzzle velocities, including at different temperatures. That's why I said you have to do your preparatory work in advance. If you are much off on that, it will compound your errors down range by a lot. Don't guess, run your load over a chronograph.

Proper accurate ranging, wind calls, accurate rifle and loads, data gathering in a range of settings, and of course your own skills make up the whole package. However, I still love old school, learning the basics first before stepping into LRFs, ballistics programs and wind meters.

 

[HodgdonExtreme]

As mentioned, you're going to need something to measure station pressure, or, even better in my opinion is an instrument that indicates DA for you, like a Kestrel.

With JBM, you can create a spreadsheet with trajectories based on: Varying DA, Varying Temperature, Varying Velocity

Personally, I set my muzzle velocity variation to zero, and create cards at 3 temperatures (30º, 60º and 90º) and DA from -2000ft to 6000ft in 1000ft increments.

I end up with a card for each DA. Each card has 3 columns on it...one column for each temperature.

 

[riffraff]

Great discussion. I am trying to do the same approach, and just now starting out. The chart below has columns for DA. The 'ZERO DA' column is ACTUAL DATA from the range. The other columns are for DAs in 2000' increments, and are calculated ESTIMATES so far. At my location (Missouri) the range is 1200' elevation. When temps are about 35 degrees, the DA is near ZERO depending on altimeter setting. Here is a handy tool:

density altitude calculator

When temps are near 65 here, the DA is near 2000', and temps above 90 make the DA about 4000'.

I will update these columns with real data as the temperatures warm up this year.

Also, I will be going to a range this summer that has DAs between 4000-6000' in hot weather (2600' elevation at the range), so decided I would build a preliminary chart as a first guess.

I used three calculators: JBM Ballistics, MD Ballistics App on an iPad, and the online Applied Ballistics Calculator, and crosschecked them all...used higher elevations for the 6k', 8k', and 10k' data.

Some apps use Relative Humidity (RH), so here is another tool:

Temperature, Dewpoint, and Relative Humidity Calculator

I may be dreaming.... we will see if this is close at all. DA accounts for may variables like elevation, temp, humidity, and altimeter setting....seems to me that DA is the key to building a good chart...others with more experience my know better.

A BIG ASSUMPTION that I make is that I am using Hodgdon H4350 powder (42.5gr pushing a Lapua 139gr Scenar at 2830fps). I am assuming that it is a temperature stable powder, and that the muzzle velocity is consistent through the temperature range(???). Muzzle velocity variation would obviously require multiple columns for these temperature variations.

Redmanss and HodgdonExtreme have more experience than me, so their comments hold more weight....I am just trying to find a good 'hasty field chart' to get me close for 'Tactical/Practical' matches. Is my approach too simplistic?

 

[eicas]

riffraff,

I like your simplicity. Like me, are you wondering why some are putting temp columns into DA calculations? Maybe I'm reading too much into your posts.

QFE, QNE, QNH

 

[Mudinyeri]

subscribed

 

[roggom]

Just get an FDAC, so much easier. Match the card to your velocity and slide. DA will change throught the day but not shot to shot.

 

[raptor99]

I use JBM to set up my cards. I dial my MOAs and I use a kestrel to get my DA. I have found that for my shooting I need to have data out to 1500yds. For my area I use DAs from 1500 to 6500ft. What I have found though is I really only need to make my extra cards( For the higher altitudes) From 700 to 1500yds because no matter the DA out to 700yds there isn't much of a difference in my dials. I have found the further out you go the more the DA makes a difference so its important to know you DA if you shooting past 700yds.

This has worked well for me and has proven very accurate. My son in law uses a ballistic app off of his phone that tells him what to dial and we are always within .5moa for what the data calls for between us. No matter what you use if your shooting past 700yds in different conditions you need to know the DA.

 

[riffraff]

eicas -

Yes, I agree that temperature columns are not required, because the muzzle velocity is so consistent with H4350.

roggom - FDAC is great (I have one), but the advantage of my card is that it will be ACTUAL data instead of computed data when I get a chance to fill it in as the weather warms up. As they say,'the bullet doesn't lie'. In a 'designated marksman' competition where you must shoot multiple distances in the same stage it is much quicker to interpolate off the chart instead of spinning each shot, right? And I write each of the holds on the back of my hand for quick reference, hopefully the quickest way to get the shot on target? ...plus, our targets tend to be 2+ MOA and engaged from barricades, or prone with a time limit, so speed of engagement is a factor.

When I go to the range, I compute DA for various projected temperatures during the day, so that I can interpolate off the chart quickly as long as I know the temperature and the trend of the altimeter setting. Just my two cents worth, but I am a new guy.

raptor99 - yes, I have seen the same thing, my charts above show there is not much difference until you get to 400 or 500 yards....after that, BIG differences.

Again, my emphasis is engaging multiple targets at multiple distances in minimum time (designated marksman).....ymmv, lots of good techniques discussed here.

Buzz

 

[remr5]

true your mv at a minimum of 600 yds and look at a whiz wheel from Accuracy 1st

 

[Scurvydog]

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