Small bullets will start to tumble, and come down relatively slowly, whereas larger bullets can maintain their stabilizing rotation and come down much faster. bullet shape, air density and cross- sectional area), so M dropping out of the above equation is merely illusionary.īecause air resistance depends largely on surface area whilst weight depends on volume, larger bullets will drop faster than smaller bullets. Actually, the ballistic coeficient itself depends on mass (among several other things, e.g. The mass of the bullet (M) drops out of the equation, which at first may seem strange, since mass clearly should have an effect on terminal velocity. M = mass of object m2 = ballistic coeficient g = gravity v = velocity. When the forces are balanced, Table 3.6 Maximum altitude attained by various rounds.

It is easy to calculate this terminal velocity if the drag coefficient is known. When any object falls through the atmosphere, eventually, the retarding force of drag will balance with gravity, and the object's terminal velocity will be reached. The ability to calculate the actual terminal velocity of a missile could, therefore, be critical to the investigation. The terminal velocity of a missile is obviously much more relevant to the investigator as any bullet fired vertically into the air will come down with potential wounding capability. There are, however, a vast number of hunting cartridges which would be equally capable of reaching this altitude. The above table indicates, from the limited data available, that only the 30-06 or 0.303 rounds would have sufficient initial velocity to reach an airliner flying at 9000 feet. The results of some actual test firings are tabulated as follows (Table 3.6): Hatcher carried out a similar set of experiments using the 30-06 rifle round.Ī very simple rule of thumb to calculate the maximum altitude that a bullet will reach is that it will be approximately f the maximum horizontal range. In 1909, Major Hardcastle fired a number of rounds vertically into the air and shortly after World War I, Julian S.

The question was, therefore, what weapon could have fired a bullet with sufficient velocity to reach the altitude of 9000 ft at which the airliner was flying. Unfortunately, the airline concerned was unwilling to have the tailfin dismantled and taken apart due to the costs involved, and it was not possible to determine the exact calibre of weapon used. There was an occasion, however, when a commercial airliner which had been flying in the air space above Northern Ireland was found, on landing, to have a 7.62 mm calibre hole in one side of the tailfin. As with many other subjects that one comes across in forensic firearms examinations, this has little real relevance in everyday case examinations.

Can a falling bullet penetrate a roof