DEMIGOD LLC > Ballistic Data Cards
Accurate trajectory data is key to long-range shooting. The DEMIGOD LLC data cards are a culmination of several years of practical long-range shooting combined with an understanding of the data flow required to make shots in the field. The information you need is all there in a simple format to reduce "brain" error, with no extra information that can cause confusion in the field and under stress. I recommend keeping a set of data cards for each rifle and load which correspond to the different environmental conditions in which the rifle will be used. Different environmental conditions are tracked using Density Altitude (click for explanation).

Cards are thermally laminated to make them waterproof. I punch a single hole in the right-hand edge and tie the card to my forward scope ring. Alternatively, I can punch the top, or leave a margin of lamination- you can punch it yourself for some other mounting technique. For 1000-yard cards, the front side has data for 100 to 520, and the back side continues with 540 to 1000. The card is formatted like this:
6.5 123 @ 2930 fps
(100yd) 8000' DA
    0.1  100  0.0
    0.1  120  0.0
    0.2  140  0.1
 1" 0.2  160  0.2
 1" 0.2  180  0.2
 1" 0.2  200  0.3
 2" 0.3  220  0.4
 2" 0.3  240  0.6
The third column is the distance in yards. Based on the range of the current target, move one column to the right (column four) for the drop correction. Go one column left (column two) for the windage correction in MILs/MOA. The first column is the wind correction in inches, but is only present if it's less than one foot. This is based on the idea that "Kentucky" windage becomes less precise when you start to get a ways off the target. All windage correction values are based on a 10 mph cross-wind.

The header of the card has a caliber/load identifier along with the muzzle velocity. The second line shows the zero distance and Density Altitude conditions for the card.

DEMIGOD LLC ballistic data cards are available for all common long-range loads, or you can send me the relevant rifle setup and load parameters and get a custom set of cards.

223 - 77SMK - 2600 fps,
308 - 175SMK - 2650 fps,
308 - 155 Scenar - 2875 fps
260 - 139 Scenar - 2800 fps
260 - 142 SMK - 2800 fps
300WM - 190 SMK - 2950 fps
338LM - 250 Scenar - 2950 fps
... select MOA or MILs, select low-altitude or high-altitude set.

Standard card sets have data out to 1000 yards every 20 yards, with a 100-yard zero to minimize zero-shift based on atmospheric changes. Low-altitude sets have data for -2000, 0, 2000, 4000, and 6000' Density Altitude, and are recommended if your station alttude is 3000' or lower.. High-altitude sets have data for 4000, 6000, 8000, 10000, and 12000' Density Altitude, and are recommended if your station altitude is 4000' or higher.

PRICE - A standard set of five cards is $50 plus $5 S&H for USPS Priority Mail shipping. $55/set delivered.

STEP 1. Select caliber - bullet - velocity, for example: 308 - 175SMK - 2650
STEP 2. Specify yards or meters.
STEP 3. Specify scope center over bore center distance in inches: averages 1.75".
STEP 4. Specify zero distance: 100 yards recommended
STEP 5. Select maximum range in yards and interval, for example: to 1000 yards in 20-yard increments.
STEP 6. Select the angular units you want the dope values in: MOA, MILS, or SMOA/IPHY.
STEP 7. Select the Density Altitudes where you want data, for example: 0, 2000, 4000, and 6000'.

PRICE - Custom card sets have a $10 setup fee, $10/card, plus $5 S&H for USPS Priority Mail shipping. For example: $65 for a five-card set, delivered.

Each order includes a color-coded matrix to estimate the local Density Altitude from station altitude and ambient temperature, or you can read the Density Altitude from the Kestrel 4000.

Email for a quote and payment instructions, or give me a call during weekday evenings. PayPal preferred.

Density Altitude
For the last three years, I have been using Density Altitude as the primary index to characterize atmospheric conditions.

From: Windmeters and Environmental Stations for Tactical Shooting (Guns & Ammo's Tactical Guns & Gear, December 2006):
   Environmental conditions are often described in terms of pressure, temperature, and humidity. Pressure is reported both as "station pressure", which is the actual barometer reading, or as a corrected number normalized to sea level based on the actual location altitude. With these three numbers, the shooter can cross-reference similar conditions in his log book, or he can use the parameters as input to a ballistic program to generate the drop values for his load.
  Keeping track of three independent parameters can be confusing. For a log-book, the shooter can end up with a lot of different environmental conditions, which are hard to match. If he runs data from one of the ballistic programs, he will have to sweep three variables to generate data for all likely conditions. There is also an overlap in pressure and temperature mapping to air density. For example, a cold 20-degree day in Denver will have about the same air density as a hot 95-degree day in Dallas.
  One solution to this is a figure called "density altitude." Density altitude is one number that represents the density of the air, which is all the bullet cares about anyway, and it effectively replaces the need for the three original parameters.
  The best way to utilize density altitude is to get the current value off one of the wind-meters that reports it, and use that as an index into the data-book or input into the ballistic program. With less technology, the shooter can cross-reference the location altitude with temperature to get a pretty accurate estimate of the density altitude.

My data cards are all indexed by Density Altitude. Simply choose the Density Altitude(s) at which you shoot, and then get a set of cards for those conditions. When you set out for a training session or match, simply look at the expected station altitude and temperature and select the right card from your deck.

Here is a Printable table which gives you the average Density Altitude for a particular altitude and temperature.

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