Air Rifle Outer Ballistics

PRELIMINARY REMARK:

The term "Ballistics" represents the "science of the movement of projectiles". This special chapter deals more with the movement of bullets, i. e. with all possible physical parameters like speed. energy, bullet trajectory etc.. Basically it is distinguished between "inner ballistics", "outer ballistics" and "target ballistics". The first deals with all processes which take place within a gun to drive a bullet through the barrel bore. In a firearm this is the ignition and combustion of the gunpowder, the resulting increase of pressure and the movement of the bullet until reaching the muzzle. In an airgun these phenomena are somewhat different according to the type (precharged or spring piston) which will be explained a little bit more in detail in the section "Airgun Secrets". The target ballistics describe the effects of the bullet hit at the target and is not of essential relevance here. The real focus of interest in the context of this chapter is solely outer ballistics, i. e. everything which happens after the bullet left the muzzle. There are "ballistical tables" in which one can find such parameters but currently there are much better tools available for that purpose. Those can be found in a big selection of computer programs which can be used to perform very special calculations for the own rifle or handgun and the corresponding ammunition provided that some special data are available. Plenty of those programs one can obtain free of any costs but they are mostly relatively simple. Nevertheless, in many cases they are suitable for "daily common utilization" of an airgun. More sophisticated software has a price and one should contemplate well if they are suitable for airgun ballistics and especially FTS and if the investments will pay off. In the following text corresponding links, advices and remarks will be given.

THEORETICAL BASICS  & PRACTICAL HINTS:

I am sure that it is useful  to know some common and special theoretical basic knowledge. I have not to do that myself because there is a pretty good information in the internet which arose from the never resting brain of Ian Pellant who took care intensively of air rifle ballistics and who offers a nice special airgun ballistics software at  http://www.hsv.tis.net/~ispellan/Software.html . Simply read his manuscript at http://www.hsv.tis.net/~ispellan/AirgunBC.html to understand the Newtonian equation and the "secrets of the inverse square". Ian does not care about a parameter called "Ballistical Coefficient" (BC) which may be subject of serious disputes. So, I recommend to neglect this part of his manuscript until you studied what I have to report later. Ian presents some good arguments why one may neglect the BC in air rifle ballistics and in his opinion it is only of relevance for artillery. As a reloader I know very well that this is not really true to that extend because the BC is essential for precise calculations of bullet trajectories of firearms. But: if you look at an airgun pellet and compare it with a 0.30 caliber centerfire rifle bullet or with the model projectile on which nearly all ballistical software is based there will be some drastic differences. The BCs of pellets range between 0.0100 and 0.0350 which is much, much lower tan those of centerfire rifle bullets. Jim Bauman, a true Guru of airgun ballistics in the U. S. A. has a totally different opinion than Ian Pellant. He is strongly convinced that the BC is extremely important for airgun ballistics. He wrote a very special air rifle ballistics program which he sells for U. S. $ 65.- together with an excellent manual and the booklet "Pellets and Ballistics". I strongly recommend to visit the homepage of his "Lame Rabbit" Company where not only the software is explained but also a counterfeit of Jim and plenty of very useful information about airgun ballistics can be found. So: visit immediately  http://ourworld.compuserve.com/homepages/LameRabbit/ !

Jim Bauman developed an admirable method to determine the speed of pellets at two different points of distance and so he was able to calculate the BCs of nearly all available pellets. His software is -as far as I know- the only one which allows the input of BCs with 4 decimals. I will report more about this later.

That's enough. Because nearly nobody calculates currently ballistical tables on paper or with a pocket calculator the previous text and the links are at least only of academic interest. Nevertheless, it may be useful to have this basic knowledge which, in addition, may help to handle special terms in ballistical computer programs.

COMPUTER PROGRAMS TO CALCULATE BALLISTICAL DATA:

There are plenty of free ballistics computer programs which one may download from the Internet. A really comprehensive collection of those is found on the Italian/German homepage  "Ballistik. I tested most of these and was not very much impressed. I want to present here four programs and to mention a fifth one without extended personal experiences. I own this software and played around and compared a lot with the four I mentioned initially. My statements are, naturally, subjective because I am no ballistics expert. Nevertheless, I am an experienced reloader and hobby-ballistican which likes it very much  to compare the results of computer calculations with the rough reality. But now let's come to details.

At first some basic terms should be explained. In most of the ballistics programs one is able to obtain the following results: bullet trajectory, flight height to sight line, drop height to sight line, drop, velocity, energy and wind deviation. The last three terms have not to be explained but the remaining are not glass-clear at a first glance. The following picture may help to understand them better.

The first software I will report on is AIRGUN 7.0 written by Ian Pellant. As mentioned  already above one obtains it easily and free of any costs by download from http://www.hsv.tis.net/~ispellan/Software.html . The program runs 30 days if it is not registered. Registration is also free and Ian only wants to know who uses his program. One receives an email with a registration number and everything is o. k.. In my opinion this software is good. It is running under Windows 95/98. It calculates trajectory, velocity and energy which may be displayed as tables or graphs. Moreover a table with minutes of angle (MOA) is available for scope correction. The most common pellets are collected in a pellet list which can be edited. One may select metrical or imperial units, which is a great advantage for all "non-imperials". An additional module serves for the production of different targets which can be printed in good quality as it is also the case for the tables and graphs. A nice special is the possibility to read in data obtained with a CHRONY-Chronograph (for details see later) directly via the serial port. A support module serves for the proper CHRONY settings. So, that's a lot for nothing. Naturally, the question about the performance of that freeware arises. I performed plenty of experiments and comparisons and so I am able to say that there is nor reason for AIRGUN 7.0 to hide. The calculated values, however, are ever somewhat lower than those obtained with other programs. As often in life also here the truth seems to be somewhere in between. Comprehensive practical shooting tests showed that the other programs mostly brought slightly higher values than those resulting from the tests. In my opinion AIRGUN 7.0 is a good solution.

The next software I want to refer is Air Rifle Ballistics written by Jim Bauman. Also this program runs -as all the others- under Windows 95/98. It is not free and must be purchased for about US$ 65.- which is wholesale even when bearing in mind the tremendous high exchange rate of the American currency in most European countries. A first impression of the abilities of this software can be found at http://ourworld.compuserve.com/homepages/LameRabbit/ . When purchasing it I recommend to send Jim an email and to make an agreement with him to pack the money in cash in a letter to be sent with registered mail because checks and money orders for overseas are horribly expensive. This software has an excellent user surface and contains all functions of a "real" ballistical computer program. That means that it may be also utilized by reloaders of centerfire ammunition. Graphs can be edited and printed with Paintbrush in a good quality. The most valuable advantage is  the comprehensive collection of BCs in the tremendous pellet list which you can obtain -as far as I know- nowhere else on the world. Another excellent feature is that BCs can be inserted with 4 decimals which is important especially for airgun ballistics. A disadvantage for non-imperial users is that the data are all in the imperial format but Jim corrected this in the latest version. I do not yet have the update but I will report about it after I received it. The included booklet "Pellets and Ballistics" is a treasure trove for the beginner and experienced airgun ballistics enthusiast. I learned a lot from it! It is the proof that Jim Bauman is in fact a "Ballistics Guru". I use ARB95 frequently with pleasure and I fully recommend it.

Ballistics software number 3 in the VISIER SHOT 2.01 which is sold by the international weapon magazine VISIER for wholesale DM 92.-. It's a real bargain because the ballistics part is only one of four (competition, ballistics, effect, parameters). The software uses BCs and it contains a database of bullets which contains also a lot of different pellets and which may be edited. The graphs are excellent and offer the possibility to mark different functions or lines with different colors. It is an advantage that different graphs can be shown in one picture for easy comparison. There is a special text editor included which serves for nice and informative (which depends naturally on the user's inputs) title sheets. A disadvantage for non-German.-speaking/reading shooters is that the program is written in German. I can be switched, however, from metric to imperial units and vice versa. A nice speciality is a module which offers the possibility to visualize the hits as red spots from different distances on target sheets. There are some samples included but one can easily introduce own targets via a scanner. Unfortunately, this "hit pictures" cannot be printed (possibly it will work with "printscreen" but I never tried that).   I love this software very much and can recommend it fully, too. To purchase it contact the following address: Paul Parey Zeitschriftenverlag GmbH & Co. KG, VISIER-Leserservice, Postfach 1363, D-56373 Nassau. Email: vertrieb@paulparey.de . Free Hotline (Mo - Fr 8 - 18 hours CET: 0800-7285727).

The last ballistics software I want to present here is "QuickTarget" written by H. Broemel. This is not available separately because it is an appendix of the inner ballistics program "QuickLoad". This package produces a little bit bigger hole in the pocket because it is more expensive than its competitors. Some time ago I paid about DM 300.- for it. For a serious reloader this software absolutely is a MUST and the investment easily pays off. Concerning QickTarget the author himself mentions that there would be better software on the market but I believe that this is an understatement. In my opinion this program is the best one on the German market and it has all features ones heart desires. In addition, the printouts of the results including graphs are more than excellent and informative. In the following picture an example is given  which demonstrates this. One has the choice between several different options. Also this program offers the possibility to visualize the hits from different distances on various   

normal and grid targets comfortably in a variable scale. With this the prefixed reticle correction in clicks, the wind drift and the effect of canting is shown. Moreover, there is a choice between different reticles. This pictures can be easily printed. Unfortunately, there is no possibility to bring in own targets but because of the universal grid targets this is negligible. This program is in my opinion the "Rolls Royce" of the ballistics computer programs. It may be ordered directly from the author Dipl.-Ing. H. Broemel. Schopenhauerstraße 18, D-63303 Dreieich. As far as I know this software is also available from the  Kettner company. 

At "Waffen Online" one can download from "Software zum Download" free another ballistics software named "Projektil" written by R. Becker which uses BCs. I did not have the time for comprehensive tests up to today but at a first glance the results obtained with it are good. It produces nice graphs and I will report about it here as soon as I have some more experiences with it.

In the internet there is also a page called  "Ballistik für Schützen und Jäger"  (ballistics for shooters and hunters). It is worth to have a look on it.  

All these ballistics computer programs are good for nothing if one does not obtain special basic data. The bullet or pellet weight can be determined easily but the difficulties mostly start with the measurement of the muzzle velocity. To do this one needs a chronograph (better: chronoscope) which enables the shooter to perform that. These devices will be mentioned later but let me tell here that they cost between 100.- and several thousands of DM.

VBs PERSONAL REMARKS: 

In my personal opinion all these computer programs are only valuable for special freaks which like to perform many experiments and tests. I wrote this page because I am a member of this guild but for practical FT shooting they should not be overestimated. What does a shooter do when he determines with his/her scope and air rifle the aiming points at different distances? He/she establishes a ballistical table! This he/she may do for several pellet brands and for a second and a third rifle but then he/she completed the task. The wind compensation problem is a special science at all. Who carries around permanently an equipment to determine the exact wind speed and direction? In this case practical experience counts much more than theoretical calculations.

In general: in my opinion air rifle ballistics are only well known up to distances of 50 m. It is well known that the pellet is forced by the barrel twist to a rotation which stabilizes the trajectory. It lasts a certain time of flight if this rotation is stable and one is then able to punch nice round holes into paper with a 12 ftp air rifle at a distance of 50 m. If one tries that at 100 m distance this results -provided the target is hit at all- in less exact holes and partially in "mushrooms" which are proof that the pellet had left its stable rotating flight and made a 90 degree turn. If one has a look on a corresponding ballistical computer calculation one easily will recognize that the pellet has to have a flight distance of about 150 m. So, for me and some others this is suspect. The aerodynamical not very suitable pellets seem to loose their stable flight in the second half of the trajectory and to touch the ground earlier than calculations predict. Practical experiments to clear this up definitively are difficult and the only realistic solution is the utilization of a high speed camera to catch pictures of the pellets in flight. But how can this be done when it is unknown where to position the camera? Jim Bauman reported me in an email about an interesting experiment. The shooting place of his club is located at the shore of a lake and on the other side in a distance of about 300 yards there are houses the inhabitants of which  were afraid to be hit by the pellets. So, a strong air rifle was shot with different angles of elevation over the lake and observed where the pellet went into the water surface which was easily to recognize. The maximum distance was about 150 yards. If one looks on computer calculations the pellets fired from, e. g., a 15 ftp air rifle should fly more than 220 yards but this is obviously wrong. I performed similar experiments which show without any doubt that the pellets do not fly so far as the computer calculations tell us. O. k., FT is shot on distances of 50 m maximally and why should it be important what's happening thereafter? If there is a safe backstop at the range this is really true. If not, it is important to have a safety area which is long enough and for that it is important to know how far the pellets fly. I know that shooting range experts in Germany currently deal with this problem and they seem not to believe me. In my opinion this question must be answered by serious and comprehensive practical test performed by "real" experts. 

APPENDIX: CHRONOGRAPHS, CHRONOSCOPES:

As mentioned already above special devices, chronographs (called better chronoscopes because they mostly display visually what they measured and calculated), are essential for the determination of the muzzle velocity. In general the measuring electronic components are light-sensitive, e. g. photo transistors, which are able to detect a pellet when it passes it. Infra red barriers are another possibility. If two of such components are arranged in a certain distance they can be used to measure the time a bullet or pellet needs to pass the space between them and to determine so the flight in m/sec or ft/sec. If the first sensor unit is placed directly at the muzzle (which is easy with an airgun) the Vo can be determined directly without difficulties. Even wholesale chronscopes offer an astonishingly high amount of different functions. They store series of shots, calculate the standard deviation, the average of all measurements etc. etc. They mostly have an interface so that the data can be sent directly into a computer. 

I personally possess two of such devices. The first is a CHRONY Beta. The CHRONY devices are available as different models for prices between DM 100.- and 400.-. I bought mine some years ago from the HEGE-Zeughaus.  In contrast to other persons I had only good experiences with it. The data obtained with it withstand the comparison with those from much more expensive chronoscopes easily. It is simple to handle and its construction is robust. It digested without serious damage or loss of functionality close pellet hits. An obvious disadvantage is that the CHRONY does not work indoors with European fluorescent lamps. For me this is not of importance because I perform my experiments mostly in the open air with fine weather. Under the roof it is easy to use car  bulbs or halogen lamps together with a direct current power supply..  

A very beautiful and innovative chronoscope developed especially for airguns is the COMBRO-cb-625 . This very tiny instrument is fixed with a rubber band and an adjustable connector directly at the muzzle. The measuring distance is only 6.5 cm and the pellet passes two infrared barriers which makes one independent from the illumination. The power is supplied by two small "knob" batteries. The display is integrated in he device and shows Vo or Eo according to the preset adjustment. There is the choice between metrical and imperial units. A nice special is the possibility to store in the COMBRO a legal power limit (e. g. 12 ftp). If the measurement exceeds this value "ILLEGAL" appears in the display screen. Initially I was a little bit sceptical because of the short measuring distance but the results obtained are in fact comparable to the CHRONY. I ever would prefer the latter for larger series of measurements but for the rapid test on the range (e. g. to control the legality of an airgun for a competition) the first is simply ideal. The COMBRO-cb-625 costs about DM 150.- in Germany but in GB it is (despite of the horrible exchange rate of the British currency) much more wholesale: about DM 100.- including postage and handling. The device has a serial port computer interface and a connection cable is available for about DM 27.-. For do-it-yourself a wiring plan is available free. The corresponding software can be downloaded from the link given above. I like this dwarf chronoscope very much and it is a permanent component of my shooting equipment.

Another chronoscope which I did not use myself up to today but which is highly recommended by experts is the CED Millenium Chronograph which is available for DM 450.- from IFS Shooting Supplies, Gartenstraße 16, 56727 St. Johann, Tel. 02657-71553, Fax ....-71554. The leading chronograph company in the U.S.A. is the OEHLER company.

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