.177 caliber or 4.5 mm caliber is the smallest diameter of
pellets and
BB shots widely used in
air guns, and is the only caliber generally accepted for formal target competition. It is also sometimes used for hunting small game, like fowl. It is also used in
field target competitions, where it competes with 5 mm (.20 caliber) and
.22 caliber (5.5 mm) rifles.
Steel BBs are typically slightly smaller than lead BBs at diameter, although the bore diameter of the
barrel
A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, ...
are the same. Some air guns are designed to accept .177 pellets, .177 lead shot, or .175 steel BBs interchangeably.
Relationship between caliber and trajectory
If two guns fire pellets of different weights, the gun firing the lighter pellet must fire it at a higher velocity to achieve the same
muzzle energy
Muzzle energy is the kinetic energy of a bullet as it is expelled from the muzzle of a firearm. Without consideration of factors such as aerodynamics and gravity for the sake of comparison, muzzle energy is used as a rough indication of the des ...
. This is an important consideration in locations where air guns are
legally restricted by muzzle energy. Because a .177 pellet is lighter than a larger caliber pellet of similar design, the .177 pellet can be propelled faster and therefore on a flatter
trajectory
A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete tr ...
, without exceeding the legal limit on energy. However, because the lighter projectile has a lower
ballistic coefficient
In ballistics, the ballistic coefficient (BC, ''C'') of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration: a high number indicates a low negative acceleration—the ...
, it loses its initial energy to air resistance faster than a heavier, slower pellet. Therefore, a heavier pellet (typically of a larger caliber) may be preferred for hunting.
External links
Information on .177 air rifle pelletsInformation on .177 pellets
See also
*
4 mm caliber
*
Air gun
*
Pellet (air gun)
A pellet is a non-spherical projectile designed to be shot from an air gun, and an airgun that shoots such pellets is commonly known as a pellet gun. Air gun pellets differ from bullets and shot used in firearms in terms of the pressures enco ...
*
177 (number)
Pistol and rifle cartridges
{{ammo-stub