ELD® Match and ELD-X® Ballistic Coefficient Changes
Hornady originally published “800 yard”* average Ballistic Coefficient (BC) values for ELD-X and ELD Match bullets. This was done to provide the most usable BC from a trajectory prediction standpoint. Unfortunately many shooters did not understand that Hornady was listing a more useable “800 yard” BC while other manufacturers list “200 yard”* BCs. When doing pre-purchase research either on the web or at the store, the increased performance of the ELD Match and ELD-X bullets wasn’t always realized in a head-to-head BC comparison. Hornady will now publish “200 yard” (Mach 2.25 / 2,512 fps @ ICAO Standard Atmosphere**) G1 and G7 Ballistic Coefficient (BC) numbers for all ELD-X and ELD Match bullets. Mach 2.0 (2,233 fps @ ICAO Standard Atmosphere) and Mach 1.75 (1,954 fps @ ICAO Standard Atmosphere) BC values will also be available on the Hornady website (www.hornady.com/BC). As Hornady moves the industry to drag coefficient based trajectory calculations for these types of projectiles (www.hornady.com/4dof) the Ballistic Coefficient is becoming somewhat irrelevant except for those still using BC based trajectory calculators or when using BC as a rating criteria for bullet performance.
Ballistic Coefficient (BC) values at Mach 2.25 (2512 fps @ ICAO Standard Atmosphere) should be used when comparing to other published BC values within the industry. Ballistic Coefficient values at Mach 1.75 (1954 fps @ ICAO Standard Atmosphere), should be used when calculating trajectories for shooting beyond 600 yds. Ballistic Coefficient values at Mach 2.0 and 1.75 offer comparisons to other manufacturers that publish multiple BC’s based on velocity.
In addition to the change listed above, a select few ELD-X and ELD Match bullets initially had BC values that were determined from prototype bullets. As Hornady moved into production of these bullets, the BC value increased (a positive gain) due to the improvements in the manufacturing process from R&D to production machinery.
*The Science Behind It
Ballistic Coefficient (BC) values can, and usually do change in value with changes in velocity. Most bullets exhibit a lowering BC as velocity slows. The extent of how much a BC will change depends on each unique bullet shape. When comparing BC’s of different bullets, it is important to use an apples to apples approach. To do this, bullets should be compared at a given Mach number (Mach 1 = 1116.48 fps @ ICAO Standard Atmosphere). Mach number is the velocity of the bullet divided by the speed of sound. If a Mach number is unavailable, velocity can be used if the BC’s are corrected to Standard Atmosphere which is fairly typical practice within the industry. The majority of industry published BC’s are measured over relatively short ranges of 100 -300 yards which corresponds to velocities around 2500 fps depending on muzzle velocities. Some manufacturers offer BC values at different velocity ranges.
** Hornady BC values have been corrected back to International Civil Aviation Organization (ICAO) Standard Atmosphere (Sea Level, 59 degrees F, 29.92 inHg, 0% Humidity).