12-18-2020, 07:02 AM
From your post it seems like you have most of the variables covered. There was a recent post on this forum where accuracy went bad and was restored to good when the copper in the barrel returned after 50? rounds, some barrels like a good amount of copper.
I am assuming you are doing tests at various seating depths (distances from the lands). I recently came across a interview with David Tubbs on load development and one thing he said jumped out at me, if there is vertical dispersion he would change the powder charge, for horizontal dispersion he would change the bullet seating depth.
Lastly, some barrels just don't like some bullets. The chronograph results might tell if the vertical dispersion was due to large velocity spreads or not and was due to something else like barrel harmonics.
Oh, if there is a muzzle device, even a thread protector be sure to check it's not in a loose state.
I am assuming you are doing tests at various seating depths (distances from the lands). I recently came across a interview with David Tubbs on load development and one thing he said jumped out at me, if there is vertical dispersion he would change the powder charge, for horizontal dispersion he would change the bullet seating depth.
Lastly, some barrels just don't like some bullets. The chronograph results might tell if the vertical dispersion was due to large velocity spreads or not and was due to something else like barrel harmonics.
Oh, if there is a muzzle device, even a thread protector be sure to check it's not in a loose state.