Hornady ELD Bullet - BC science

[hollohas]

Did a search for Hornady ELD, didn't find. Seemed like this belonged in Precision rifle rather than the ballistics sub-forum, so here it is. It was a toss-up, please move if I was wrong.

New product from Hornady that does some pretty significant things for bullet BC. They used doppler radar and found that long range, poly-tip bullets actually have a significant degradation in BC over long range and high velocity. In short, the tips were MELTING. Air temps also had a major effect on BC...it gets worse at high air temps. This means BC is different for the very same bullets at different air temps. Apparently this is true of ALL current poly-tip bullets.

They made a new tip, that doesn't melt and for the long range precision crowd, looks like it might be a huge deal. You can read all the extensive science behind it yourselves (very data/science intensive report linked below), but here is a brief highlight.

http://www.hornady.com/assets/files/...al_Details.pdf

While analyzing the radar data on the new bullet, Hornady engineers noticed something right away that was puzzling. In Drag Coefficient versus Mach (Cd vs Mach) graphs, they saw that the new projectile was gaining drag shortly after leaving the barrel, which affected the performance of that bullet for the rest of its flight path. Simply put, the bullet acted like it had one particular BC for the first 100 to 150 yards, then transitioned to a lower BC for the rest of its flight path. Further testing was done with other bullets including BTHP match and A-Max bullets. While the BTHP bullets Cd vs Mach charts looked as expected, the A-Max bullets were showing the same increase in drag that the prototype hunting bullet did. It was as if the bullet was changing shape in flight.

Further testing was done to confirm suspicions that the polymer tip was the culprit. Aerodynamically efficient, high BC bullets at high velocity were suffering from polymer tips softening and deforming in flight. Further testing proved that it happens to all conventional polymer tipped bullets, regardless of manufacturer. Tipped varmint bullets and conventional low to medium BC (sub .550 G1) bullets are not significantly affected. They simply do not hold a high velocity long enough for the aerodynamic heating to significantly affect their tip.

The Hornady 6.5mm 140gr A-Max is a very popular match bullet. Its long-time published G1 BC of .585 has been measured with chronographs at the muzzle, 100 and 200 yards. The radar verifies that exact BC out to 200 yards. When fired at 800 yards; however, the radar verified average BC it is actually .545. This is because of the polymer tip melting and deforming during flight. When the traditional tip is replaced with a Heat Shield tip, the Radar verified 800 yard average BC becomes .610 – a huge improvement! Why a .610 when we already established a 200 yard BC of .585? The .610 BC shows that the traditional tip was already exhibiting degradation at 200 yards.

Pretty interesting, huh?

https://youtu.be/VY3CKco6rqc