Water pressure is 44 lbs/sq in at 100 ft depth! That is .44 PSI at 1 ft depth! Your 45LC has less area than 1 sq in! IF the water depth in your washer is 1 ft(?) your cartridge had less than .44 psi exerted on it(not much) I would be more concerned about the coating on your powder, which controls the burning rate, being effected due to the tumbling action. This effect is worst on a cartridge that is less than full! This brings new meaning to the term "squib load" !
jcelect