Guide

G1 vs G7: Two Standard Bullets, Two Rulers

A ballistic coefficient is a comparison, not a property. It says: this bullet loses velocity like the standard bullet would, scaled by this factor. G1 and G7 are two different standard bullets — the G1 is a flat-base spitzer from the artillery era; the G7 is a long boat-tail that looks like a modern match bullet. Same physical bullet, two rulers, two numbers.

Why the numbers differ so much

For a typical match bullet the G7 BC is roughly half the G1 BC (a 140 gr Hybrid: G1 .607, G7 .311). Neither is "the real one." What matters is which standard's drag curve shape matches your bullet across the speeds it will actually fly. A long boat-tail's drag falls off with speed almost exactly like the G7 standard, so a single G7 BC predicts well from muzzle to transonic. The same bullet on the G1 ruler needs a different BC at different speeds — which is why Sierra publishes its MatchKing BCs in velocity bands, and Hornady publishes three Mach-banded sets.

Rules that keep you out of trouble

• Never mix rulers. A G1 BC in a G7 calculation is a garbage trajectory. Every TruingLog tool makes you pick the model next to the number.
• Prefer G7 for long boat-tails beyond ~600 yards, where the transonic drag rise decides the drop.
• G1 is fine — and often better documented — for flat-base and short-range bullets, and it's the only model Sierra bands.
• Converting is estimating. There is no constant ratio. Our converter matches the 1,000-yard drop of a full trajectory run and labels the result an estimate; whenever the manufacturer publishes both numbers, theirs govern.
• Mind the source. Retailer listings mislabel BCs in the wild — during our library research we caught a G7 value printed as a "G1" (which would have doubled a bullet's predicted drag). Every value in the library names the manufacturer publication it came from.

The practical test

Run your bullet both ways in the trajectory calculator. Inside 500 yards the two models usually agree within a click or two. At 1,000 yards, on a boat-tail, trust the model whose standard looks like your bullet — G7 — and then true it to your rifle anyway.