Density Altitude (DA) Charts by “Solo”

Today we are going to discuss density altitude charts and why they are useful to the Modern Day Shooter, whether you are an enthusiast, competitor, hunter, or professional sniper!

Okay so this is a finished Density Altitude (DA) Chart for those who do not play around with Density Altitude much or at all.

First things first to break down DA is a very simple process to understand, textbook definition:

Formally defined as “pressure altitude corrected for nonstandard temperature variations.”

Basically, this means for us as shooters that Density Altitude is the altitude that our projectile "thinks" it is as while is performs through the air. So even though we are shooting at 400 feet mean sea level (MSL), the atmospherics effect our bullet in a manner which makes it perform as though it was at a different altitude.

So, to show how this works, I built a chart for my current rifle build. Normally my charts go all the way to 15k DA, but for this I am using it as a learning tool, so 10k DA gets the point across for everyone to understand.

This is for 175g SMK HPBT @ 2714 fps MV.

So basically, I build an all-encompassing chart on a spread sheet, I do this by manipulating my AB Kestrel to equal each DA I need then plug in the range card data in each column as depicted below.

I write them out to the nearest hundredth, I do this first so I can get a feel for the actual numbers I am going to be working with later in the development of the chart.

So once I have built this all the way out I go through and mark where I see a shift that is in my personal opinion going to require me making a conscious correction. For me this is a two tenths of a mil shift. I highlighted it in red so it is easy to locate through the whole chart. Either in the form of dial data onto my elevation turret or holding either of which works. You can make your own assumption on what amount of deviation you think is where you need to make a change, everyone is different so find what works best for you!

Once I have done that I go through and find the total deviation in elevation from ZERO to 10K DA (or whatever DA you max at).

For every single range I have inserted in my chart, again for me I do every 25 yards (or meters depending on if this is for professional application or personal). I do this because I like to know what my overall deviation is and where I really need to start paying attention to changes in my bullets performance based on where I am located in the world and what I am doing.

Now we have to start making this this manageable and useable for quick reference and efficiency. So the first thing I am going to do after this is go back through every single range and DA column and round to the nearest tenth of a mil. This is a no brainer move for me because my scope is in tenth of a mil adjustments, and so there is no need to keep any numbers beyond that because I can not make adjustments that fine tuned. It just becomes more cluttered at this point for no reason. I use the general rule of thumb .05 and up goes to the higher number, .04 and below go to the lower number. After than I mark the changes in groups in different ways by colors or bold outlines so I can easily identify changes that would need to be made at different differences. I do not highlight the entire card that is because I do not want it to become so busy that I can no longer see what is happening, again it is for quick reference and usually I am taking data from this card and putting it onto another card for use.

KEYNOTE: When I manipulated my DA, I used pressure to gain/loss elevation, I know you can use any of the three variables to do so but I chose pressure. You can use whatever you like, I have not had a chance to thoroughly test which one is the most accurate because obviously each element has different effects on the bullet and can speed up or slow down our rounds differently.

But when I manipulated the temperature to compare, it was still holding true to deviations every 10 degrees of temperature in Fahrenheit. BUT AGAIN, I do not have the ability to physically go check each one of these in a real life setting currently to be sure that the information was dead to nuts accurate.

SO, I use this card to get a baseline for what I need at these different DAs as a starting point, if I can validate trajectories at these DA’s to absolutely make sure everything is as it should be!

But with this chart I can then build individual arm board DOPE charts for each DA and have them prebuilt to swap out as needed when I reach these different DAs through my operations and work environments.

Useful little tool requires some front-end prep work but in the long run it is worth it for real world applications.

I HAVE YET TO HAVE A CARD FAIL ME! That doesn’t mean you shouldn’t find your own truth and test it to whatever level you feel necessary!