question: why shooting firearms up in the air is still dangerous? Wouldn’t they lose all their velocity at some point during the travel time?
comment: Yes, they lose all their velocity once they are very high up. Then they start to fall, and quickly regain all that velocity, until you have a bullet traveling at deadly speed raining from the sky in a random location.
passages: For long to very long small arms target ranges and flight times, minor effects and forces such as the ones described in the long range factors paragraph become important and have to be taken into account. The practical effects of these minor variables are generally irrelevant for most firearms users, since normal group scatter at short and medium ranges prevails over the influence these effects exert on projectile trajectories.
   Less advanced ballistic computer programs predict the same trajectory for uphill and downhill shots at the same vertical angle and range. The more advanced programs factor in the small effect of gravity on uphill and on downhill shots resulting in slightly differing trajectories at the same vertical angle and range. No publicly available ballistic computer program currently (2017) accounts for the complicated phenomena of differing air densities the projectile encounters during flight.
  
  Section::::External factors.:Ambient air density.
   For medium to longer ranges and flight times, besides gravity, air resistance and wind, several intermediate or meso variables described in the external factors paragraph have to be taken into account for small arms. Meso variables can become significant for firearms users that have to deal with angled shot scenarios or extended ranges, but are seldom relevant at common hunting and target shooting distances.
   When in flight, the main or major forces acting on the projectile are gravity, drag, and if present, wind; if in powered flight, thrust; and if guided, the forces imparted by the control surfaces.
   A somewhat less obvious effect is caused by head or tailwinds. A headwind will slightly increase the relative velocity of the projectile, and increase drag and the corresponding drop. A tailwind will reduce the drag and the projectile/bullet drop. In the real world, pure head or tailwinds are rare, since wind is seldomly constant in force and direction and normally interacts with the terrain it is blowing over. This often makes ultra long range shooting in head or tailwind conditions difficult.
  
  Section::::External factors.:Vertical angles.
   Precision shooting at such small targets lends itself to dialing in elevation adjustments and for the most part when shooting at high power Kentucky windage a bit less of a factor than with although time-of-flight is the primary factor for windage and, while the power of guns used may be lower, lighter pellets are also used in such guns and the speed of a pellet at the muzzle is only a bit slower (7.2 grains at versus , for example). Hence, windage is a similar problem for those shooting at either power in most instances.
   Though not forces acting on projectile trajectories there are some equipment related factors that influence trajectories. Since these factors can cause otherwise unexplainable external ballistic flight behavior they have to be briefly mentioned.
  
  Section::::Equipment factors.:Lateral jump.
  
  Lateral jump is caused by a slight lateral and rotational movement of a gun barrel at the instant of firing. It has the effect of a small error in bearing. The effect is ignored, since it is small and varies from round to round.
  
  Section::::Equipment factors.:Lateral throw-off.
   Space warfare tactics are also affected by the Big Sky Theory, if unguided projectiles are used. At the vast engagement distances, the subtended angle of the target would be minuscule, and the projectile flight time to target would be great, possibly on the order of an hour or more. If the target vehicle randomly maneuvered every few minutes, the chance of a hit would be extremely small, even if many projectiles were fired. A space weapon using unguided kinetic projectiles flew on the Soviet Almaz military space station.
  
  Section::::Big ocean theory.
   In small arms external ballistics applications, gravity imparts a downward acceleration on the projectile, causing it to drop from the line of sight. Drag, or the air resistance, decelerates the projectile with a force proportional to the square of the velocity. Wind makes the projectile deviate from its trajectory. During flight, gravity, drag, and wind have a major impact on the path of the projectile, and must be accounted for when predicting how the projectile will travel.
   At extremely long ranges, artillery must fire projectiles along trajectories that are not even approximately straight; they are closer to parabolic, although air resistance affects this. Extreme long range projectiles are subject to significant deflections, depending on circumstances, from the line toward the target; and all external factors and long range factors must be taken into account when aiming. In super gun artillery cases, like the Paris gun, very subtle relativistic effects that are not covered in this article can further refine aiming solutions.
   BULLET::::- Spindrift, an effect caused by the rotation of the bullet
  
  BULLET::::- Coriolis effect, caused by the Earth's rotation
  
  BULLET::::- Mirage, which causes the shooter to hit high and to the side if there is a little wind
  
  BULLET::::- Angle to the target (called "cosine angle"), either up or downhill
  
  etc.
  
  All these parameters can also be used at shorter distances, but the effect they pose is so small that they generally can be disregarded. At short distances the accuracy of the shooter, rifle and ammunition will often mask the very small effect these factors will have.
   The magnitude of the Coriolis effect is small. For small arms, the magnitude of the Coriolis effect is generally insignificant (for high powered rifles in the order of about at ), but for ballistic projectiles with long flight times, such as extreme long-range rifle projectiles, artillery, and rockets like intercontinental ballistic missiles, it is a significant factor in calculating the trajectory. The magnitude of the drift depends on the firing and target location, azimuth of firing, projectile velocity and time of flight.
  
  Section::::Long range factors.:Coriolis drift.:Horizontal effect.
   The mathematical prediction models available for inclined fire scenarios, depending on the amount and direction (uphill or downhill) of the inclination angle and range, yield varying accuracy expectation levels.
   Depending on the rifle, bullets typically travel between 800 and 1000 m/s (2600 and 3400 feet per second) at the moment they leave the rifle's barrel. The bullet slows down considerably due to friction with the air over a distance. The distance a bullet will travel is determined by its shape, weight, launch velocity and launch angle as with any projectile, the study of which is referred to as external ballistics.
   BULLET::::- In accordance with a police request, the Federal Aviation Administration imposes a no-fly zone covering a 3.4-mile (5.5-km) radius around Ferguson, Missouri, because of ongoing racial unrest there, extending to an altitude of 5,000 feet (1,524 meters). By the morning of 12 August, the altitude limit will be reduced to 3,000 feet (914 meters) to avoid interference with traffic at Lambert–St. Louis International Airport.
  
  BULLET::::- 13 August
   BULLET::::- Above 34000 ft: M0.83
  
  With their higher performance characteristics, military aircraft have higher holding speed limits.
  
  In Canada, the speeds are:
  
  BULLET::::- All propeller including turboprop aircraft – MHA to :
  
  BULLET::::- Civilian Jet – MHA to :
  
  BULLET::::- Above 14000 ft:
  
  BULLET::::- turboprop – normal climb speed
  
  BULLET::::- Jet aircraft – maximum
  
  "MHA – Minimum Holding Altitude"
  
  Section::::Timing corrections.
  
  To achieve a one-minute inbound leg, there are two commonly used ways to modify timings:
   The above variations can be explained by differences in the ambient air density used for these BC statements or differing range-speed measurements on which the stated G1 BC averages are based. The BC changes during a projectile's flight and stated BC's are always averages for particular range-speed regimes. Some more explanation about the transient nature of a projectile's G1 BC (it rises above or gets under a stated average value for a certain speed-range regime) during flight can be found at the external ballistics article. This article implies that knowing how a BC was established is almost as important as knowing the stated BC value itself.
   The total time t for which the projectile remains in the air is called the time of flight.
  
  After the flight, the projectile returns to the horizontal axis (x-axis), so formula_23.
  
  Note that we have neglected air resistance on the projectile.
  
  If the starting point is at height y with respect to the point of impact, the time of flight is:
  
  As above, this expression can be reduced to
  
  if θ is 45° and y is 0.
  
  Section::::Maximum height of projectile.
  
  The greatest height that the object will reach is known as the peak of the object's motion.
   Typically the trajectory height would not be greater than 4.5 inches at and the rifle would have a muzzle velocity of at least . While is not fast by modern standards, it was in the era of black powder and spherical balls. As nitro powders were introduced and became the standard, bores grew smaller, and velocities grew ever larger, until the term "express" grew to mean something other than just high velocity. William Greener, for example, splits British sporting rifles at the turn of the 20th century into four classes:
  
  BULLET::::- Large bore smoothbores, or "Elephant guns"
   Section::::Calculation of trajectory.
  
  To succeed at long range shooting, one must have good shooting skill fundamentals, a rifle with good precision and as consistent ammunition as possible (mainly to achieve a consistent muzzle velocity). In addition, a variety of external factors must be taken into account with regard to ballistics calculation, including:
  
  BULLET::::- Wind (both by the shooter and along the whole flight path to the target).
  
  BULLET::::- Bullet shape and weight, trying to achieve the highest possible ballistic coefficient ("BC")
  
  BULLET::::- Air pressure, altitude and (to a certain degree) humidity
  
  BULLET::::- Temperature (including air, ammunition and barrel temperature)
   The tables below are based on the sections (12, 24, 36 and 48 inches) of the original Second Class Figure target placed at 300 yards, and shows the same relative target sizes for different ranges. The military service ammunition from that time (such as .303 British, .30-06 Springfield, 6.5×55mm, 8x57mm etc.) were more high powered and less prone to suffer from wind drift compared to modern military intermediate cartridge (such as 5.56 NATO, 5.45×39mm, 5.8×42mm, etc.). With the high powered calibers wind drift will barely be noticeable at 100 m, slightly more at 200 m and will only become a small factor at 300 m.
   In the first few centimeters of travel down the bore, the bullet reaches a significant percentage of its final velocity, even for high-capacity rifles, with slow burning powder. The acceleration is on the order of tens of thousands of gravities, so even a projectile as light as can provide over of resistance due to inertia. Changes in bullet mass, therefore, have a huge impact on the pressure curves of smokeless powder cartridges, unlike black-powder cartridges. The loading or reloading of smokeless cartridges thus requires high-precision equipment, and carefully measured tables of load data for given cartridges, powders, and bullet weights.
   BULLET::::- A gunman firing at the street from an apartment window in San Diego, California, under the approach path to San Diego International Airport prompts the U.S. Federal Aviation Administration to halt landings at the airport; the lack of arriving flights also affects departures, although departures continue during the incident. The gunman surrenders after more than five hours, by which time 30 arriving and departing flights have been cancelled and 30 other flights have been diverted to other airports.
  
  BULLET::::- 5 November
   BULLET::::- 0.40 g
  
  BULLET::::- 0.45 g
  
  BULLET::::- 0.48 g
  
  BULLET::::- 0.50 g
  
  BULLET::::- 0.90 g — Heaviest mass
  
  Section::::Flight physics.
  
  Section::::Flight physics.:Pellet muzzle velocity and energy.
  
  The pellet speed of spring-powered and automatic electric guns is determined in large part by the tension of the gun's main spring. Muzzle velocity limits are between for AEGs and for single-shot spring sniper rifles.
   /div
  
  Section::::References.
  
  BULLET::::- ("Google Books")
  
  BULLET::::- (various backdated issues relating to Modern Air Transport, 1960–1975)
  
  Section::::External links.
  
  BULLET::::- Aviation Safety Network database - Modern Air Transport accidents/incidents
  
  BULLET::::- Modern Air Transport Curtiss Super 46C Commando N3935C resting on the ramp at Greater Rochester International Airport in upstate New York during 1960.
  
  BULLET::::- Modern Air Transport Lockheed L-049D Constellation N86531 resting on the ramp at Denver Stapleton during June 1965.
  
  BULLET::::- Modern Air Transport Douglas DC-7C Seven Seas N381M resting on the ramp at Fort Lauderdale Executive during July 1968.
  
presuppositions: Shooting up should not be dangerous. A firearm loses its velocity when shot up in the air.
corrections: The bullets speed back up on the way down and can hit someone. A firearm regains any velocity lost when it was shot up in the air on the way down.
raw_presuppositions: Shooting up should not be dangerous. A firearm loses its velocity when shot up in the air.
raw_corrections: The bullets speed back up on the way down and can hit someone. A firearm regains any velocity lost when it was shot up in the air on the way down.