This started off as a Ruger MK III .22  pistol.  We wanted to thread the barrel to accommodate a suppressor but still allow the guns use without one.

This is the finished result.  The sight has been moved back to allow for extra room. The barrel has been thread and also includes an in house fabricated screw on thread protector.  This allows the pistol to be fired without a suppressor and keep the threads safe from harm.