The Beretta 680 series over under with removable and replaceable side thingies is an example of a useless extra that actually does what it is advertised to do when fitted properly. When fitted properly, the barrels are actually cammed toward the breech and stay in the cammed position while in the firing position. You can actually feel the barrels tightening up against the cams as you close the gun. On guns without the replaceable cams, or on guns with barrels that did not come on the action being used, you can't usually feel the beginning of the camming action. The camming action is so slight that the trunnion contact is not lightened to any extent and you have full contact at both the cam and the trunnions. The 680 series action is so "correct" that the fitted thingies are not used in lower end guns and their longevity record is as good as the more expensive models. Kind of like Purdeys with and without side clips and third fasteners. By the Beretta action being "correct", I mean that the trunnions and the cams only serve to add to the locking lugs that protrude from the receiver and plug into the barrel breeches. I think the gun could be safely fired with any two of the features deactivated. It would be an interesting experiment.
