Had the same with a New Haven Model 70 Classic in 338WM.
To bore sight it, the rear ring had to be adjusted until it’s edge was level with the bases edge on the left side. I zeroed the scope reticle 3 times, thinking that was somehow off...nope, barrel was crooked against the action face.
Pulled the barrel, barrel shoulder AND threads were way off centre. The outside of the barrel contour was also off the same amount as everything else, so the bore was also not in the centre of the barrel contour.
The action only required a little truing prior to fitting a new button rifled barrel.
Cheers.
Winchester was know for this seen one or two, you kinda wonder how that got past quality control
