G1 vs G7: Choosing the Right Ballistic Coefficient

Ballistic coefficient is the single number that tells your solver how well a bullet fights the air. Get it wrong — or pair it with the wrong drag model — and an otherwise perfect setup will miss at distance. Here's what BC actually means, and how to pick between G1 and G7.

What ballistic coefficient really measures

Ballistic coefficient (BC) describes how efficiently a bullet retains velocity as it flies. A higher BC means less drag relative to the bullet's mass, so it slows down more slowly, drops less, and drifts less in the wind. Two bullets can leave the muzzle at the same speed and arrive at 1000 yards hundreds of feet-per-second apart — that gap is BC at work.

The number itself is a ratio: it compares your bullet's drag to a standard reference projectile. That comparison only makes sense if you know which reference you're comparing against — and that's exactly what "G1" and "G7" specify.

Drag models: G1 and G7

A drag model is the shape of the reference bullet whose drag curve your BC is scaled against:

• G1 is a flat-based reference with a relatively short, blunt nose. It loosely resembles older flat-base hunting bullets.
• G7 is a long, boat-tailed reference with a sleek secant ogive — the shape of a modern long-range match bullet.

Here's the crucial part: a G1 BC and a G7 BC for the same bullet are different numbers and are not interchangeable. A bullet might carry a G1 BC of 0.530 and a G7 BC of 0.270. If you enter a G7 number but tell the solver it's G1, your trajectory will be badly wrong.

Why G7 fits long-range bullets better

The reason serious shooters prefer G7 for match bullets is that the G7 reference shape is close to the real bullet's shape. When the reference and the projectile look alike, a single BC value tracks the real drag curve across a wide velocity band — from supersonic out through transonic.

With G1, a sleek boat-tail bullet doesn't match the stubby reference, so its "BC" isn't really constant — it changes with velocity. That's why you'll sometimes see G1 BCs published as banded values ("0.540 above 2600 fps, 0.520 from 2600–2100…"). G7 mostly sidesteps this for VLD-style bullets, giving you one stable number.

So which should you use?

• Modern boat-tail / match / VLD bullets: use G7 when a G7 BC is available. It will hold up better at extended range and through the transonic zone.
• Flat-base, round-nose, or older hunting bullets: G1 is usually the only published number and is a perfectly good fit for those shapes.
• When in doubt: use whatever model the manufacturer used to publish the BC you have. Consistency between number and model beats theory.

The part the BC can't fix: true it

Published BCs are measured under controlled conditions with a specific barrel and lot of ammunition. Yours will differ slightly. The most reliable workflow is to start with the published BC and model, shoot at a known distance well into your trajectory, and adjust BC (or muzzle velocity) until the solver matches your real impacts. That process — truing — is what turns a good prediction into a dependable one.

Strelok Pro carries both G1 and G7 BCs for 75+ bullets and lets you switch models and edit values per profile, so you can dial in the exact combination your rifle prints.