I've shot a lot of guns on my plate to test regulation.
Stan I thought you told me you just got your plate...
I'm a stickler for shooting the steel pattern plate at my gun club...shot it today matter of fact.
I've owned and shot a lot of vintage English SxSs...I never ran across one the was not regulated left and right some were high and low because of the stock.
Never shot one that "changed season to season" a test I never worried about...maybe Stan is onto something.
I can't see how that's even possible.
To alleviate the chance of having a seasonally regulated shotgun I guess it's best to pattern right before each season.
Maybe Stan Will elaborate.