February 5, 2023. This article was one the TOP 20 most-read Daily Bulletin articles for the past 12 months. For those who missed it, we’re republishing it today. The diagram above is a TiborasurasRex YouTube video that compares G1 and G7 BC models. CLICK HERE to view the video. The most up-to-date ballistics software allows you to choose between G1 and G7 Ballistic Coefficients (BC) values for calculating a trajectory. The body’s ballistic coefficient (BC), is a measure its ability to overcome air resistance during flight. G7 values are typically numerically lower than G1 for the same bullet. However, this doesn’t mean that you should choose a G1 value just because it is more expensive. One forum member wrote: “I went to the JBM Ballistics website in order to use the web-based Trajectory calculator, and when I reached the section that allows you to choose between G1 or G7 BC, it was confusing. Which one or how do you choose? The G1 vs. the G7 Ballistic Coefficients – Which is Right for You?
G1 and G7 are aerodynamic drag models that are based on specific projectile shapes. The G1 shape is similar to a flat-based bullet. G7 is a different shape and more closely resembles a modern long-range round bullet. G1 is preferred for flat-based bullets, whereas G7 is more suitable for long-range bullets with a longer tail.
Many ballistics programs offer only the G1 drag model. Bryan Litz, author Applied Ballistics for Long Range Shooting believes that the G7 standard is better for long-range, low drag bullets. “Part of why there’s so much’slop in advertised BCs is that they’re referencing the G1 standard, which is very speed sensitive. G7 is better suited for long-range bullets. Here are the results of my testing with two long-range, low-drag boat-tail bullets. You can compare the G1 BCs and G7 Ballistic coefficients.
Berger 180 VLD: 0.659 lb/in?
JLK 180: 0.645 Lb/in? The reason the BC for JLK is lower is that the meplat on the lot I tested was significantly higher (0.075?). vs. 0.059 vs 0.059? These BCs are consistent for all speeds and are referenced to G7 standards.
Berger 180 VLD: 0.337 lb/in?
JLK 180: 0.330lb/in Bryan says that these BCs are more suitable for long-range bullets when they are available. [Editor’s Note: BCs are usually reported as a 0.XXX number. The lb/in The lb/in tag is applicable to all BCs but is often left off for simplicity.
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