Barrel whip can throw the same bullet to two sweet spots at different velocities. The first (lower velocity) shot may be whipping the muzzle down slightly and giving you a stable muzzle exit at with the muzzle low. The higher velocity may be throwing your groups higher. This gives you a different number to calculate BC than the 'accurate' number. You'd have to check velocity at multiple points on the trajectory and see if the velocity is dropping with the BC.
Miles,How?Delta V ?T.I.A.Hunter
One other thing I thought about last night was that the slugs could be leaving the muzzle at a smaller angle of yaw at 1100 fps than at 1000, and/or may be settling down better because they are closer to Mach 1 (for some reason).... A slug travelling straight will always have less drag than one skidding sideways, and in addition will be more accurate as well.... In fact, the smaller groups at 1100 fps probably indicate less yaw, which should indeed produce a better BC....Bob
What about luck of the draw, more favorable barrel harmonics at 1100 FPS, producing tighter groups?Ditto for barrel harmonics contributing to a higher than expected POI?
Quote from: rsterne on August 18, 2022, 12:45:27 PMOne other thing I thought about last night was that the slugs could be leaving the muzzle at a smaller angle of yaw at 1100 fps than at 1000, and/or may be settling down better because they are closer to Mach 1 (for some reason).... A slug travelling straight will always have less drag than one skidding sideways, and in addition will be more accurate as well.... In fact, the smaller groups at 1100 fps probably indicate less yaw, which should indeed produce a better BC....BobIf that is indeed a reason, and I agree that the smaller groups may indicate less yaw, it would suggest that the slugs are somewhat over stable at the lower speed since the gyroscopic stability will be less at the higher speed. It could also be down to dynamic stability being superior at the higher speed but that seems a bit of a long shot.