Originally Posted by Big Uncle

TNLW,

I have seen something similar when someone was loading a bit too close to the lands and probably getting some pressure spikes. Also, sometimes different lots of bullets have very tiny variations from previous lots which can change max coal.

Your coal if fairly long, so I would try pressing the bullet deeper and see if that has any effect. Sometimes a bit of jump is not a bad thing.

Are you showing a six shot group with mixed results, or two three shot groups with different POI?