GEAR REVIEW: Field Density Altitude Compensator
by Ian Kenney
A week before the fall Allegheny Sniper Challenge (ASC), I first saw Adaptive’s Field Density Altitude Compensator (FDAC). I was impressed by its capabilities and compact size and I managed to take one home from the ASC prize table the very next weekend. The FDAC comes from Adaptive Consulting and Training Services in Stafford, VA. The guys at Adaptive know a thing or two about long-range shooting — many of them are former USMC Scout Snipers. Their long-range shooting and combat experience helped them perfect the FDAC.
At first glance the $39.95 FDAC appears to be just another data card. However, in a number of ways, it is completely different than traditional data cards. The FDAC was designed to be simple and accurate, so that any military or civilian shooter could pick it up and, within minutes, effectively employ it. Anyone familiar with a Midot Master should find the FDAC simple and intuitive. Another plus is that, unlike electronic gadgets, the FDAC doesn’t need batteries or shielding from the elements. You don’t have to carry around extra batteries, chargers, and “ruggedized” weather-proof cases.
FDAC Offers Multiple Cards for More Precise Solutions
The FDAC is quite different than traditional data cards that calculate trajectories based on a single muzzle velocity in a given set of conditions. The problem with those traditional data cards is that, as soon as one variable changes, the card’s ballistic solution becomes less valid. The FDAC solves this problem by employing several cards for different muzzle velocities and using Density Dltitude to compensate for the differences in environmental conditions. For the uninitiated, Density Altitude combines the temperature, humidity, barometric pressure, and elevation figures into one number that is more easily used over a wider range of conditions. Density Altitude can be obtained with a portable weather station (such as a Kestrel). If a portable weather meter is not available, the basic chart printed on the card itself works pretty well even when guessing at the physical altitude and temperature.
CLICK HERE for FDAC Users’ Guide PDF
FDAC Ballistic Solutions Deliver First-Round Hits in the Field
I first tested the FDAC at Reade Range in Pennsylvania, shooting from 500 to 1000 yards. I used the 2700 fps velocity card that came with my FDAC for the 175 Sierra Match King since that most closely matched what I had loaded up. Starting out with a cold bore shot from the 500-yard line, I obtained the density altitude using my Brunton ADC Pro, and slid the card over until the proper density altitude column was showing. With 3.2 mils of elevation and .2 mils of left wind dialed into my Nightforce 3.5-15×50 (first focal plane) scope, I went for my cold bore shot, hoping the FDAC would put me close. I was happily rewarded with a first round, center mass hit, just a little left of center.
The FDAC continued to shine at longer ranges. FDAC solutions gave me first-round hits at 600 and 800 yards, a second round hit at 1000 yards. Several weeks later I found myself in a field in rural North Carolina once again putting the FDAC to good use this time without any electronic aids. To my surprise, my guestimate of about 500’ for density altitude was pretty darn close to what the Kestrel my friend had was saying also. Just like at Reade Range, the FDAC values delivered cold bore hits that were nearly point of aim = point of impact. That demonstrated how well the FDAC worked in warm weather.
This winter I was able to see how the FDAC performed in cold conditions. In cooler, denser air, a bullet requires more elevation correction to get on target than it would need in warmer temps. So I went out one chilly January morning and confirmed that the FDAC can handle cold conditions. The FDAC solutions once again gave me first round hits from 250 yards to 730 yards. The little DA chart put me in the right vicinity for density altitude just by knowing my altitude and making a guess for the air temperature. Since I’ve started using the FDAC I’ve found that the data is either spot on or within about .2 mils of the correct dope at nearly all distances when using the correct density altitude column. This is very impressive. I found that the FDAC delivered practically the same data as popular digital PDAs and field ballistic calculators. But the FDAC can be even faster in use (once you become familiar with its operation), and, at $39.95, it costs a fraction of what a dedicated electronic ballistics solver would cost. The FDAC is practical, very accurate, inexpensive, compact, lightweight and never needs batteries — what’s not to like?
Below is a SnipersHide Video Review of the FDAC Tool
New Enhanced Milspec FDAC Released this Year
Adaptive has put much R&D into the FDAC and it shows. Thousands of Field Density Altitude Compensators have been provided to soldiers and marines, who are making good use of the devices. At the 2011 SHOT Show, Adaptive unveiled an enhanced FDAC, the MILSPEC-XR. This new version includes a new Density Altitude calculator, extended range dope for the .338LM and .300WM, as well as tools for slope dope and moving targets. Adaptive also offers conversion tables and compatibility charts so that the FDAC can be used with other bullets besides the original FDAC default projectiles. (For FDAC owners, the conversion charts are FREE!) The FDAC is truly one of those few products that I wish I had when I was deployed to Afghanistan. I highly recommend it to any long-range shooter using .308 Win, .300WM or .338LM cartridges (with a mil-based optic). For more information, or to order an FDAC tool, visit the Adaptive website, ACTSVirginia.com, or call (540) 657-8541.
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Tags: Allegheny, ballistics, Density Altitude, Mil Raidian, Mildot Master, SnipersHide
The advantage seems supposedly that it doesn’t need batteries..
But you need to measure with a battery powered Kestrel, or guess the parameters,,Right?
What was the advantage again?
That was used to prove it correct. It’s not needed, just makes it more precise.
Paper maps, Google earth, etc will have altitude available to you if you research the area you will be shooting in first.
A thermometer can be had cheap or guess the temp or look around for a thermometer where you are at. My shooting range has three, my truck has one and I can usually guess within few degrees without one until it’s below 20… It’s just like judging wind speeds, practice makes you more accurate at interpreting the conditions.
There is a DA chart on the back, all you need to know is what altitude your at and temp is, no Kestrel is needed, but a Kestrel is more accurite, you can also use the FDAC even if your bullets are going faster or slower than the charts provided, I add\subtract 1000 DA for every 25FPS, this seems to work great with my 175smk load going 2750, I sure wish they made DA cards for 139 Scenars and 140 Amax.
All I’m sayin is that you are building in a lot of errors with this shortcut -that isn’t really.
Anyone who uses their Kestrel knows that pressure, altitude, and especially DA, don’t actually correlate well.
Just take a moment to use it and see for yourself.. There is more to DA and air density than altitude and temp.
And of coarse BDC charts are a joke compared to local ballistic solutions with software.
All this guessing(how many guesses here?), looking up, holding off, and eventually accepting the reduction of capabilities, saves nothing over actual measurement(map,compass,LRF,Kestrel), field calculations(any ballistic calculator), and dialing in(with scope turrets) for better accuracy.
You’re putting yourselves ear deep in tactical delusions here.
Umm…Maybe you should actually do the two years of R&D that we did during the development of the product, or the 20,000 rounds of ammo we fired all around the world, now combine that with a bunch of actual experience working a bolt gun on a two way range. Maybe spend your youth in the infantry, become a Marine Sniper, become the Chief Instructor of USMC Scout Sniper School.
We have over 2,000 FDAC’s in theater right now, we get daily emails from young men that have been entrusted to hit what they shoot at that thank us for a product that works flawlessly for them.
Computers are great, but they often weigh as much as a radio battery that you might need for stuff like, oh I don’t know…a medevac, maybe some close-air support. But I’m not too sure, i’m delusional.
I used this today with my Remington tactical 308. I am impressed!
My 175smk load is right at 2550 +/- a couple feet per second. I knew the temp was in the 80’s and my range is a few feet short of 1000′. I applied the temp and altitude and came up with a DA of 2000′. Slid the card to +2k and started pulling the trigger. I shot from 500y to 1000y, at this velocity my load was subsonic at 975y. My impacts were a 1/4 minute low at 5&6 hundred, dead nuts on at 7-9 and 1000 was 1/4 minute high. That is much better than my preprinted tables I usually take with me!
This FDAC is awesome product, I am very impressed!
Will FDAC work w/ a 65. Grendel cartridge…123gr Scenar?
The FDAC works extremely well with the 123gn Lapua Scenar, simply insert the FDAC slide that is 50fps faster than your 123gn Scenar load, you can only do this with the 123gn Scenar upto about 2650 fps, because our fastest slide in the 175 SMK kit is for 2700 fps.
If you ever have a technical question, feel free to contact us at info@actsvirginia.com and we’ll be glad to answer any questions that you have about our product line.
Mike, I hate to correct you, but as a pilot and rifleman I can tell you that there is nothing more to DA than altitude and temperature. DA is nothing more than the current altitude (or barometric pressure if you are flying an aircraft and get the local BM from ATIS or flight following) corrected for temperature. Those are the only two variables need known to correct for Density Altitude.
Not only is the FDAC a great piece of kit, but the customer serive that comes with the FDAC is far above average.