my 21 is just slightly harder to open when both barrels have been fired, but not difficult. Check your primers to see if there is a drag mark on 1 of them. You could also take the barrels off, pull the trigger with a block of wood or a quarter against the firing pin hole, now compare how far the firing pins protrude. Don't try this unless you know how and are comfortable recocking the hammer without the forearm on.

This ain't a dress rehearsal , Don't Let the Old Man IN