Key operated pin tumbler locks and methodology

Apparatus and associated methodology are provided for key operated pin tumbler locks, some of which may incorporate a removable core pin tumbler lock. A selected tumbler of a type commonly used in pin tumbler locks is configured along with a driver pin to control operation of a retainer that, when rotated by use of a control key inserted in the lock, allows alternate selective removal and replacement of the core assembly in the lock. Also, or separate therefrom, one or more tumbler holes may be formed or drilled in a manner so as to prevent engagement of a tumbler with the bite of a key. Presently disclosed structures and associated methodology help to reduce any susceptibility to unauthorized techniques practiced against the lock, such as unintentional activation of the tumblers by unauthorized persons through use of a key with so-called "bumping" techniques.