A barrel crown and lands at the end of the barrel really do matter. I cut a 308 barrel down to 18 1/4” and used an annular cutting jig to rethread the barrel. After I finished crowning, I took the rifle out and shot it. Cold bore shots were dead on, but as I continued shooting the bullets would drift left.
After messing with different bullet weights and powder charges I finally discovered that I had messed up the lands at the end of the barrel because I used the bore guide wrong on the annular cutter.
I swapped barrels to a barrel I know is good and I’m back to consistent groups.


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