Thread: 300 WM load development

I would normally tell ya brass should be good for 10-15, or more firings unless you're thrashing velocity. Maybe also less for the magnum chamberings. Loose primer pockets will tell you.
The brass flow/internal volume difference across firings is irrelevant, from a ballistic standpoint.

Since you're comfortable you can shoot sub-moa, it would indicate fault with the rifle. (Might pay to Have someone else shoot a powder-charge ladder-over-chrony, just to check)
Most likely would be crown, stock screw torque/barrel float, optic mounting/optic, trigger?? bipod?