Recall on Ruger Mk IV pistols

Ruger recently discovered that all Mark IV™ pistols (including 22/45™ models) manufactured prior to June 1, 2017 have the potential to discharge unintentionally if the safety is not utilized correctly. In particular, if the trigger is pulled while the safety lever is midway between the "safe" and "fire" positions (that is, the safety is not fully engaged or fully disengaged), then the pistol may not fire when the trigger is pulled. However, if the trigger is released and the safety lever is then moved from the mid position to the "fire" position, the pistol may fire at that time.
Some are not subject to the recall; how to tell if yours is and all the other information here.