A gun lock for receiving and clamping a cross-sectional portion of a firearm. A slide bar is provided for mounting the gun lock to a surface in a storage location such as a motor vehicle, home, office, a cabinet or any surface where a gun might be stored. A locking assembly slidably mountable to the slide bar is provided. A pivotably attachable ratchet arm which resembles typical handcuffs is provided. One arm has a plurality of ratchet teeth that enables the gun lock to clamp a wide variety of cross-sectional portions of weapons having different configurations. A solenoid activatable locking assembly is positioned within the lock. The solenoid has a plunger adapted to engage one of the ratchet teeth of the ratchet arm to lock the rotatable ratchet arm in position around the cross-sectional portion of the weapon to be locked. The solenoid locking assembly is releasable via a switch. A manual override assembly is also provided. The manual override assembly is activated with a key. Once the key is turned, a camlock that is connected to the plunger of the solenoid locking assembly causes the plunger to move. When the key is turned in one direction, the arm rotates and the plunger disengages from the ratchet teeth of the ratchet arm. When the key is turned in the opposite direction, the plunger again engages one of the ratchet teeth to again lock the locking assembly. A set screw assembly for releasably locking the locking assembly onto the sliding bar is provided. A set screw and a set screw nut locks the locking assembly onto the slide bar. The set screw is accessible by a hex key through an opening in housing of the apparatus only when the ratchet arm is in the unlocked open position.