That's very interesting. I'd always thought of tuning a load as trying to arrange for the bullet to leave the muzzle at the peak (or valley) of the barrel deflection so that the impact point is insensitive to small velocity variations. I hadn't thought about catching the barrel on the upswing so it somewhat compensates for the variations or on the downswing where it exaggerates the variations. I guess my thinking was about 90 degrees out of phase with reality. Not the first time that's happened, for sure.
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