Wads may be tight and snug in a hull, but they must be tight and snug in the bore to avoid blow by. AA cases tend to have fairly thick walls, and so smaller internal diameter; wads that fit a AA case snugly may not be very snug in the bore. I personally use reiffenhauser style cases because they are thin-walled and have a greater capacity for bulky BP; AAs have a fairly small capacity at the powder end. Oversize wads still have enough give in them that they ought not increase pressures much. How much do you manage to fit in a AA hull? the times I've tried I couldn't get much, and had to use a short wad column.
Diagnosing blow-by? velocities would give clues; recovered wads may too.
RG
