Using the Leica HD-B Ballistic calculator "ABC" (Advanced Ballistic Compensation)
If you don't currently own a Leica HD-B - BisonTactical typically has them for sale!
This post explores how to setup and configure the new Leica Geovid HD-B ballistics software to generate click values in MILS for US shooters engaging targets to 1000 yards (or 925 M). This is primarily aimed at Precision rifle competitors, Tactical shooters and long range hunters who use a variety of equipment to calculate their shooting solution, and already have DOPE (not the Colorado kind) aka drop charts for their load.
The goal is to get the HD-B to match up with your known good drop charts so that you can use the Custom load ballistic data in the Leica HD-B out to its maximum distance (1000 yards).
Some preliminary information about my example setup:
- Bullet = 139 grain Lapua Scenar
- Cartridge = .260 Remington @ 2881 fps
- Rifle = DTA SRS A1 zeroed @ 100 yards w/ sight height = 2.45"
- Barrel = Short Action Customs Bartlein 26" w/ 8 twist
- Chronograph = MagnetoSpeed V3
- Environmental = Temp = 87.5 F Pressure = 30.17 inHg Humidity = 17.5 %
- PC Ballistics program = Applied Ballistics Analytics
- Leica HD-B Ballistics Application page
- Covert Utility from Josh Madison (useful in unit conversions)
- Scope is a MIL value turret / reticle with .1 MIL value clicks (tenth MIL values)
Step 1 - Convert your units to Metric
Convert all your units to Metric - since we want output from the HD-B in MILs, we are going to be looking for a "Point of Impact Correction" based on 10mm click values (or .1 MIL)
Remember 1 MIL @ 100 M = 10 cm (centimeters) and so .1 MIL (common click value on MIL scopes) @ 100 M = 1 centimeter.
Finally 1 cm = 10 mm (millimeter) - which is why we want our output in 10 mm values !
Enter the Leica Geovid HD-B menu and switch your units to EU (Metric). Click and hold the menu button (secondary - not range) for over 2 sec. EU.US or US.EU will appear in the bottom of the display, and will flash. Press the range (primary) button to select EU, then press the menu button again to save. EU. should display for 4 seconds, then disappear.
Step 2 - Standardize your two Ballistic calculators
We have known good dope for the rifle. The first step is to get the Leica online Ballistic calculator to match our trusted Ballistic calculator (the one used to generate our verified drop charts).
The Leica online Ballistic calculator uses some fixed information - which you need to put into your other Ballistic calculator:
- Sight Height = 5cm (1.9685 inches)
- Air Pressure = 1024 mbar (30.24 inHg)
Input these into your ballistic calculator so that you get a new calculation for drop. You want to obtain output that allows you to convert back and forth since the Leica calculator will only give you drop in 1cm increments and you need something to compare against that.
Below my output is in inches (so I can convert to cm easily).
The next step is while using the same static information between both Ballistics calculators - compare the results.
While not horrible, our numbers don't match very well, you can see we have a drop difference of around 9.5" at 1000 M. While not terrible - we want to be closer to the same numbers.
To get the numbers to match more closely, we only have a few things we can adjust - Velocity and BC. When I tweak both - I can get the numbers to mach MUCH more closely:
While comparing 500M, 750M and 1000M between Applied Ballistics and the Leica Online numbers, I tweaked first the muzzle velocity up/down to get close on all the numbers, then moved the BC up/down one m/s and repeated until I was able to get most of my numbers to be pretty close.
Step 3 - Upload the file to the Leica HD-B
Next we need to upload the data from the Online Leica Ballistic Calculator to the SD card so we can compare live data generated using real environmental data.
In the online Leica Ballistics app select "Save to SD" and save the file to your SD card. Re-Insert your card into the Leica HD-B and head outside.
Bring your drop charts, Kestrel or any other source you use that is already verified.
Select your information based on your current environmental conditions and start comparing drops. This may take a couple of iterations to get right - but you should be pretty dang close at some point. Below is the final test I ran comparing my Kestrel with AB (and Bryan Litz's custom curve for the 139 Lapua Scenar) to the Leica output - both based on the same environmental temperatures, the left column is distance (Ranged with the Leica in Meters) the Kestrel column is the Elevation drop from the Kestrel profile in MILs and the Leica column is the drop in 1 cm blocks based on the Leica's ballistic calculations.
Step 4 - Go to the Range and shoot to verify you hit targets with the estimated drops
Stay tuned for an update on the Range session!