Picking up a box of .410 ammo at Wally World today, I noticed several boxes Winchester AA in 20 ga marked "2 1/2 dram" and "7/8 oz" shot. This is how my RST ammo for my 20 ga Flues is marked. Would the pressures here be similiar enough not to damage my old sxs? Was not sure if there was another variable I am missing in the pressure equation....

Dave