Ballistics and Predictions
As commented before, the comparison is only performed on the supersonic zone, which is a ďcomfort zoneĒ for most ballistics engines. However itís hardly a handicap at all, given the fact that 1000 yards is probably the range span where 90% of the shots are taken.
In our pattern, itís pretty evident that Lapuaís Scenar bullet is best represented in the Point Mass method by the G7 standard, which is correct since its design is best matched by the streamlined reference.
Due to their scale, the graphs are not clear enough to acceptably show the G1 & G7 curves for LoadBase 3.0, which are basically superimposed. Regrettably there is not much to do about that.
Any method to be regarded as valuable has to meet three significant conditions: be accurate, robust and practical.
ē Being accurate is an easy to understand concept, but itís a good idea to remember that all weapons shoot to an area, not to a point, since dispersion is impossible to defeat. I mention this because more often that desired, most shooters tend to view a ballistics program as inaccurate without considering the weaponís dispersion, wrong inputs and lack of basic understanding of exterior ballistics.
ē Being robust is the ability of a method to deal with a wide range of conditions and input values without having its accuracy compromised. Itís clear that a method that cannot correctly deal with non-standard conditions or different drag functions is a limited one and its weakness will then become a major obstacle for obtaining true predictions.
ē Being practical is of paramount importance. Itís related to the aptitude of the method (ballistics engine) to handle with similar ability different drag functions, because in todayís world the availability of measurements for the G7 standard (when suitable for the bullet) or Cd tables are extremely limited. Of over 3000 commercially available bullets, only a very limited set comes with measured G7 data.
It is pretty noticeable, as expected, that the Point Mass method is quite reliant on the selected Drag Model, a fact that was proven by many tests. Itís not a criticism of the method itself, since there is nothing wrong with that. But, that makes the Point Mass method not very practical, since when not coupled with the right drag model, accuracy can deteriorate significantly.
In contrast, the LoadBase 3.0 ballistics engine shows its flexibility by accurately handling either G1 or G7. Check the almost indistinguishable curves. Therefore we can say that the engine is not drag-dependent since its accuracy is not affected by the selected drag model.
In our example, the Pejsaís method is a better technique than Point Mass, since even using the G1 drag model, it exhibits less differences.
So, the final question could be: Which one is the better? I think that the answer lies in the judgement that every reader can make of the facts presented here. Iím limited to presenting them in the most unbiased way I possibly can.
The Point Mass (3DOF) method is used by the following free and commercially available ballistics programs: JBM (web), Berger, Litz, RSI, Ballistics FTE (iPhone), iSnipe (iPhone), BulletFlight (iPhone), Shooter (Android), FieldCraft (ex ABC by CheyTac), Balistika, Quick Target Unlimited, JBallistics, BigGameInfo (web) plus many others. The algorithm is well known and free computer code is available to download from the Internet.
The Pejsa method is used by the following free and commercially available ballistics programs: FFS (Field Firing Solutions), BallistiX, Dr. Pejsaís own plus some free spreadsheets like BfX. One of the typical issues that are encountered with most of the usual solutions is that they are limited to supersonic velocity values, something very critical to take into consideration when evaluating these programs. The algorithm can be studied in the books published by the author.
Gustavo Ruiz is long time enthusiast of ballistics, reloading and above all hunting big-game. He has contributed many articles for both American and foreign magazines. Professionally, he spent eight years at Microsoft. He holds a BS in Computer Science, a BS in Operations Research and an MBA. Gustavo is also a LtCdr (res) in the Argentine Navy, and is involved with the LR shooting training program of their Special Forces operators. Currently he is developing ballistics/reloading software through Patagonia Ballistics (http://www.patagoniaballistics.com), a small software development group located in Argentina.
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