Home Forums Hunting & Shooting Long Range Hunting Bullet Shape Relative to G1 and G7 at Supersonic Velocity

You're right that Sierra publishes different G1 BC values for velocities above Mach 1.2, but what Sierra and others are doing is matching the change in velocity rather than the trajectory. So here's the question, do you really care what the velocity of your bullet is to within a few percent as it strikes the target or do you care about hitting the target? If hitting the target is the goal then bullet manufactures are chasing the wrong metric.

For example, just look at the drop numbers in the opening post of this thread and notice how far off the drop for Berger's published G1 BC is at 1500 yards relative to the G7 BC and as compared to the equal TOF G1 BC. The published G1 BC is off by 21.8 inches as compared to 5.8 inches for the equal TOF G1 BC. If you were only going to publish the G1 BC, as is the case with most manufactures, which value best matches the bullet for the way it's intended to be used? If you agree it's the equal TOF G1 BC, then Ken Oehler's conclusion is correct as to how BCs should be measured.

In my example I have assumed the published G7 BC perfectly matches the actual bullet, but if Berger's published G1 BC is off by 2.6 percent from a trajectory standpoint, then their G7 BC could also be off from a trajectory standpoint. I've read Bryan's book and understand the method he uses to come up with his BC values. As with others, he's trying to match change in velocity due to drag to that of a standard projectile. He does that for four velocity ranges and then takes the simple average as the final BC number. His method produces repeatable numbers, but he and others confuse repeatability with accuracy. Ken Oehler's suggested method is to measure initial velocity and then the bullet's time of flight over 1000 or more yards for long range bullets. This allows nature itself to perfectly average the bullet's characteristics for all velocities in between. The resulting BC best matches the trajectory of an actual bullet to a given standard bullet, and thus allows for the most accurate trajectory calculations under other altitude, wind and atmospheric conditions.

Ken Oehler's method is hard for the industry to adopt because, outside the military, I don't know of too many facilities that allow 1,000 plus yard testing under controlled conditions (indoors). You can do long range testing outside as Bryan has, but then wonder later what direction the wind was coming from as Bryan did in his book (1st edition, page 119).

I speculate that a G1 BC produced by Ken Oehler's method would more accurately match the trajectory of Beger's #24530 then their published G7 BC over the velocity range most long range shooters use. If so, then I expect a G7 BC produced by Ken Oehler's method would be better still. Of course, shooters won't get better numbers if they think the current methods of producing them are the best. I applaud Beger for publishing G7 BCs, but feel there's still room for improvement.