Buckshot was consistant with evolution in the development of small arms projectiles. The use of shot evolved from the common use of small stones which were poured down a muzzle loaders barrel, replacing a solid ball projectile. This technique was used for antipersonnel applications as well as hunting small game. As availability of lead became more prevalent it was used to form "swan drops", small dribbles of lead poured into water and used in place of small stones. In the progression of the industrial developments of ammunition, small projectile molds were produced to create spherical ball ammunition for rifles and pistols. This development led to the general use of spherical shot in large calibre muskets, leading to the first standardization of buckshot ammunition.
Buckshot ammunition was first standardized during the United States Civil War of 1860-1865. Arsenal production of ammunition for both sides of the conflict produced buckshot cartridges, consisting of a load of powder under a stack of 12 spherical shot arranged in layers of 3 balls, held within a linen or paper wrap. This loading configuration has remained consistant from the time of the initial standardization during the mid 1800's to the present day, over 150 years. Buckshot was standardized for the second time during World War Two using 9 spherical shot arranged in layers of 3 balls, assembled within a brass cartridge case. The modern example of 00 buckshot differs little from the standard musket buckshot in loading, except for the self contained cartridge case with integral ignition primer, with the exception of the late addition of granulated shot buffer.
Buckshot has an aerodynamic and terminal performance far lower than high velocity fin stabilized flechette projectiles. Upon firing interior setback forces have an extreme distortion on the spherical shape of the buckshot projectile, and during flight collisions along the axis of projection add distortions. Regardless of the addition of granulated plastic buffers or flash copper plating distortion of the lead projectiles is unavoidable. This cumulative effect creates an areodynamic form which is only roughly spherical, and so distorted as to provide no consistant predictable ballistic performance for velocity, grouping or terminal effect. Being a roughly spherical form the buckshot terminal performance is graduated by the vital nature of the target structure encountered such as dense tissue or bone. The initial penitrating buckshot will create a wound channel that the remaining buckshot will pass through a target along it's initial trajectory without vectoring off the trajectory line, and resulting in a lower energy dose transmitted to the target. The ability of buckshot to traverse some dense barrier materials such as structural timber or tree limbs and branches at close range can be one positive aspect for buckshot projectiles, however this ability is of limited value at longer ranges due to the low residual energy resulting from excessive velocity loss due to non-aerodynamic deformation.
Flechettes are fin stabilized projectiles manufactured from steel, and flechette ammunition is an assembly of 19 flechettes within a conventional cartridge case. Flechette projectiles have aerodynamic and terminal performance far above conventional buckshot. Interior setback forces have little effect on flechettes upon firing, allowing the projectile to maintain it's shape and ballistic coefficent from discharge to terminal impact. The absence of distortion during firing and flight allow predictable ballistic performance for velocity, grouping and terminal effect. Flechettes have superior terminal performance to a deformed roughly spherical lead buckshot. The flechettes steel form maintains it's rigidity in flight and looses it's rigidity upon terminal impact. As the flechette travels through dense tissue and bone it will begin yaw and travel off the initial impact axis creating a wider area of trauma. Flechettes in yaw will often bend or break along the unsupported shaft portion from residual inertia, traversing sideways or hooking through the remaining tissue along the axis of impact and imparting all remaining kinetic energy to the target.
At high striking velocities each individual flechette projectile creates a expanding supersonic cavitation wound channel behind the projectile averaging 800% larger than the flechette's body diameter. This Combined with the flechettes vectoring off the trajectory axis shortly after target contact increases the area and volume of trauma on the target.The flechette projectile passes readily through foliage and deposits little energy to the vegetation because of the penitrating pointed tip and very front small surface area. When the flight path passes through vegetation, such as brush or tree branches, the flechettes may be slightly deflected with a resulting yaw or tumbling that improves immediate energy distribution on impact. Flechettes have limited ability to traverse through the dense barrier materials that may be over penitrated by buckshot, and is one consideration for flechette projectile use. This penitration effect resulting from the flechettes immediate distribution of kinetic energy may be advantageous in selective targeting for certain environments.
During the United States Vietnam War of 1965-1972 shotguns played an active role with American ground forces with buckshot and flechette ammunition actively used and evaluated for combat effectiveness. A non-scientific combat evaluation was made from May 1967 to February 1968 with flechettes, M162 00 buckshot, and XM257 #4 buckshot. There were 8000 rounds of flechette ammunition and 50,000 rounds of #4 buckshot distributed to 12 units of the US Army Vietnam, having in their posession 2439 shotguns of various types. Flechette ammunition and 00 buckshot were equally prefered by the troops over the issued XM257 #4 buckshot, which proved ineffective under combat conditions, lacking the penitration and terminal performance of either flechettes or 00 buckshot. Flechette ammunition indicated a high lethality at all ranges with several one shot kills at engagement ranges to 100 yards, flechettes were prefered by our troops equally to 00 buckshot during this testing. Adoption of a standardized shotgun flechette cartridge was made and a specification issued for flechette ammunition. The specification for flechette ammunition remained in use untill the late 1980's with the introduction of the special operations Hekler & Koch CAWS (close assault weapon system) automatic shotgun, firing high velocity steel flechettes loaded in an all brass belted cartridge case. The flechette has been proven superior in all aspects of ballistic performance for velocity, grouping, and terminal effects when compared to conventional lead buckshot.