The premise of this question isn’t entirely correct because all self-loading firearms which have reciprocating bolts experience bolt bounce to some degree. When the bolt (or bolt carrier) on a firearm slams forward into the barrel to chamber a new cartridge, the bolt (or bolt carrier) and the barrel elastically rebound off each other, sometimes multiple times, before coming to rest. Bolt bounce can be particularly pronounced in designs with very high bolt velocity or minimal (or nonexistent) locking mechanisms. Bolt bounce can be very difficult to observe in designs with low bolt velocity and locking mechanisms which require a great deal of travel to lock and unlock.