Enum BcReferenceStandard 

pub enum BcReferenceStandard {
    Icao,
    ArmyStandardMetro,
}

Which standard atmosphere a ballistic coefficient’s numeric value is referenced to (MBA-1365).

A BC is not a pure property of the bullet — it also encodes an assumed reference air density. This engine’s retardation constant (crate::constants::CD_TO_RETARD) is calibrated against the ICAO Standard Atmosphere’s sea-level density (crate::constants::ICAO_DENSITY_LB_FT3), which most modern published BCs already assume. Some vendors (notably Sierra, Hornady, and Barnes for many bullets) instead publish BCs referenced to the older, denser Army Standard Metro atmosphere (crate::constants::ASM_DENSITY_LB_FT3). Feeding an ASM-referenced BC into this engine as if it were ICAO-referenced under-predicts drag by about 1.8% — declaring ArmyStandardMetro here corrects for that exactly once, at input normalization (see crate::constants::ASM_TO_ICAO_BC and TrajectorySolver::new).

Does not apply when a custom drag table (BallisticInputs::custom_drag_table) is active: that path divides by sectional density, not a BC value, so no BC reference conversion is physically meaningful there (see BallisticInputs::bc_reference_standard_inert_warning).

Variants

Icao

The ICAO Standard Atmosphere reference density — matches this engine’s retardation constant. The default; byte-identical to pre-MBA-1365 behavior.

ArmyStandardMetro

The (older) Army Standard Metro reference density used by some vendor-published BCs (e.g. many Sierra/Hornady/Barnes bullets).

Trait Implementations

impl Clone for BcReferenceStandard

fn clone(&self) -> BcReferenceStandard

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BcReferenceStandard

impl Debug for BcReferenceStandard

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for BcReferenceStandard

fn default() -> BcReferenceStandard

Returns the “default value” for a type.

impl Eq for BcReferenceStandard

impl PartialEq for BcReferenceStandard

fn eq(&self, other: &BcReferenceStandard) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BcReferenceStandard

impl ValueEnum for BcReferenceStandard

fn value_variants<'a>() -> &'a [Self]

All possible argument values, in display order.

fn to_possible_value<'a>(&self) -> Option<PossibleValue>

The canonical argument value.

fn from_str(input: &str, ignore_case: bool) -> Result<Self, String>

Parse an argument into Self.