Okay, here it is direct from Beretta (I looked them up because I have a 9mm):
Excessive dry firing may prematurely wear out your firing pin. Therefore, Beretta does not suggest that you perform this function. If you must dry fire, it is best to fire onto a snap cap. Firing onto a spent casing is the next best alternative. Remember that when using a snap cap in an over and under, you must bump the rear of the stock to set the triggers for the 2nd shot.