The key to shooting long range with accuracy is knowing and compensating for ballistics. Ballistics programs allow you to input your specific load information (most importantly bullet ballistic coefficient and muzzle velocity) and atmospheric conditions and then, provide you with a predicted flight path. Any experienced long range marksman will know that these predictions are often very close at closer ranges (usually out to about 500yds) and usually not so close at longer ranges. Ballistic coefficients are speed dependant because they are based off a given profile, the G1 profile being the most common. If your bullet were a perfect match to the G1 profile your BC would remain the same despite the velocity. The variance with speed is so great because the G1 profile is nothing close to the profile of long range low-drag, boat-tail, bullets most popular today. The problem is well known and the better ballistic programs have compensated for this issue to some degree.
I have been using the Nightforce Exbal program for some time and I’m very happy with it. It has allowed me to make a few cold-bore shots at extreme distances that I wouldn’t otherwise be capable. I can get information on how changing atmospheric conditions will effect my dope (data on previous engagement). I have this program loaded into a palm pilot that I can use in the field (although I’m never without a written drop chart for obvious reasons). Other features include trajectory validation, point blank range analysis, target engagement, factory load data, bullet BC data, reticle analysis, scope adjustment options, target distance estimation, etc. It’s safe to say I’ve got my money’s worth from the Exbal program. With such a comprehensive program you might wonder how Exbal compensates for inaccuracies of BC’s changing with speed. They have included a multi-BC option where one can enter 5 different BC’s at 4 specific velocities (last velocity value must be at zero). This allows you to tailor your BC to match your confirmed drops in the field. Sierra Bullets provides multiple BC’s and using these will allow you to get very good data from the program right from the start. Unfortunately most bullet manufacturers don’t give multiple speed dependant BC’s. Obviously bullet BC’s don’t change suddenly at a specific velocity, so multiple BC’s isn’t a perfect fix, simply a compromise. Even so, I’ve found it possible to get an essentially perfect drop chart using the multiple BC option. When using bullets without published speed dependant BC’s you’ll be spending some time playing with the program to get your drop chart just right. It usually takes more than one long range shooting session to get everything just right.
Thanks to Sean (host of longrangeshooter.com) I recently had the opportunity to test the Lex Talus Delta IV ballistic program. Completely satisfied and very familiar with Exbal, I was honestly expecting just another ballistic program. It doesn’t take long to notice a difference when inputting basic data. When using standard G1 BC’s you will get drop charts much closer to actual numbers than with other ballistic programs. This is due to the type of compensation Delta IV uses for BC variation with velocity. They label it “DK” which is a way of calibrating BC degradation and they also claim it can be used to compensate for shooter to shooter variances in launch dynamics. I must say that the default DK settings gives me very close drop info compared with my confirmed data. I’ve found that adjusting the DK (and BC if advertised BC is off) is easier to get “perfect” drops compared with the adjustment of multiple BC’s and the velocities at which those BC’s “change”. Delta IV includes all of the options of the Exbal program mentioned above. One option of Delta missing with Exbal is the powder temperature (ammo temp). You can adjust how sensitive your powder is to temperature. I gravitate to using powders that are not particularly sensitive to temperature. I have a reasonably wide range of temperatures where my drop charts will allow hits on reasonably small targets, but there’s no getting around changes in MV due to temperature. In one competition a couple years ago, the temperature rose to over 100 degrees and I quickly discovered I was missing high. My “temperature insensitive” loads had lulled me into a false sense of security. If only I had been using Delta IV back then! Having this option will allow you to get very accurate drops even when out of your normal temperature range.
To compare these programs I did a few tests. I have some confirmed drops for a couple different rifles. I decided to input “standard” BC info (only data that’s readily available), no multiple BC’s except for Sierra bullets. I only used the default DK for Delta IV. Either program can be adjusted to match your tested drops. Obviously, I made all the elevation, atmospheric/scope height data the same. I think these examples give a good basic idea of the program capabilities. Before I get into all the specifics let me just say that there are numerous reasons this test isn’t a perfect comparison including: operator error (in using the programs and/or shooting the rifles) imperfections in my confirmed drops, difference in actual MV and measured MV, error in atmospheric condition and elevation data, group dispersion, scope calibration error (I check mine but when you dial over 50 MOA a small error will show up in drop chart data), bullet manufacturer BC inaccuracy, etc.
Test 1) 7wsm 168gr JLK @ 2910fps Advertised BC .690
500yds Actual drop 8.25 MOA 1000yds Actual drop 24.50 MOA
500yds Exbal projected drop 8.00 MOA 1000yds Exbal projected drop 23.25
500yds Delta projected drop 8.25 MOA 1000yds Delta projected drop 24.25
This test was not exactly fair to either program since the advertised BC of this JLK bullet is too high in my opinion. Delta was still very close!
Test 2) 243 win 108gr Berger BT @ 2912… Advertised BC .511
500yds Actual Drop 8.50 MOA 1000yds Actual Drop 27.75
500yds Exbal projected drop 8.50 1000yds Exbal projected drop 27.00
500yds Delta projected drop 8.50 1000yds Delta projected drop 28.25
Test 3) 308 win 175gr SMK @ 2729… Advertised BC’s .505 (2800fps+) .496 (1800-2800fps) .485 (1800fps-)
500yds Actual Drop 10.25 MOA 1000yds Actual Drop 32.75
500yds Exbal projected drop 10.00 MOA 1000yds Exbal projected drop 32.00 MOA
500yds Delta projected drop 10.75 1000yds Delta projected drop 34.00 M0A
This test illustrates how the Exbal program works with multiple BC’s.
Test 4) 338 Lapua Mag 245gr Bore Tech V3 @ 2895… Advertised BC .869
500yds Actual Drop 7.25 MOA 1000yds Actual Drop 22.00
500yds Exbal projected drop 7.25 1000yds Exbal projected drop 21.50
500yds Delta projected drop 7.25 1000yds Delta projected drop 21.75
1850yds Actual Drop 58.00
1850yds Exbal projected drop 59.00
1850yds Delta IV projected drop 57.75
This one is truly amazing. Delta was within ¼ MOA at over a mile! I wouldn’t have imagined this was possible. Now the info after using Delta IV’s DK calculating option which gives me a new DK of .4992 new drop info was
500yds 7.25 MOA
1000yds 22.00 MOA
1850yds 58.00 MOA
A quick and simple step (DK calculation) gives me an essentially perfect drop chart not just at 500yds (most on-line ballistic calculators could do that) but spot on at 1000yds and 1850yds! To say that I’m impressed with Delta IV would be an understatement.