You can adjust how sensitive your powder is to temperature. One option of Delta missing with Exbal is the powder temperature (ammo temp). Delta IV includes all of the options of the Exbal program mentioned above. 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”. I must say that the default DK settings gives me very close drop info compared with my confirmed data. 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. This is due to the type of compensation Delta IV uses for BC variation with velocity. When using standard G1 BC’s you will get drop charts much closer to actual numbers than with other ballistic programs. It doesn’t take long to notice a difference when inputting basic data. Completely satisfied and very familiar with Exbal, I was honestly expecting just another ballistic program. Thanks to Sean (host of ) I recently had the opportunity to test the Lex Talus Delta IV ballistic program. It usually takes more than one long range shooting session to get everything just right. 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. Even so, I’ve found it possible to get an essentially perfect drop chart using the multiple BC option.
Obviously bullet BC’s don’t change suddenly at a specific velocity, so multiple BC’s isn’t a perfect fix, simply a compromise. Unfortunately most bullet manufacturers don’t give multiple speed dependant BC’s. Sierra Bullets provides multiple BC’s and using these will allow you to get very good data from the program right from the start. This allows you to tailor your BC to match your confirmed drops in the field. 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). With such a comprehensive program you might wonder how Exbal compensates for inaccuracies of BC’s changing with speed. It’s safe to say I’ve got my money’s worth from the Exbal program. 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. 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). I can get information on how changing atmospheric conditions will effect my dope (data on previous engagement). It has allowed me to make a few cold-bore shots at extreme distances that I wouldn’t otherwise be capable. I have been using the Nightforce Exbal program for some time and I’m very happy with it. The problem is well known and the better ballistic programs have compensated for this issue to some degree. 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. If your bullet were a perfect match to the G1 profile your BC would remain the same despite the velocity. Ballistic coefficients are speed dependant because they are based off a given profile, the G1 profile being the most common. 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. 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. The key to shooting long range with accuracy is knowing and compensating for ballistics.
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