Trying to locate a source for this passage, wondering if some of you might recognize it:
"Percussion is the term used when a tool called a Pick Gun, or Pistolpick, is employed to directly strike the entire row of bottom pins over and over, causing an effect similar to rapping. The stacks of pins separate as they fly upward toward the pin housing, creating huge gaps between all top and bottom pins. The gun is a spring loaded mechanism with a trigger and a vice to which is affixed a long, thin needle made of spring steel. The needle is first inserted in the keyway, all the way to the rear of the plug, and the gun is held perpendicular to the face of the lock. As the trigger is pulled back, tension is built against a coiled spring inside until a point is reached where the built-up force is released suddenly, causing the needle to strike upward. Most pick guns have a knurled wheel that controls the amount of tension that is allowed to accumulate before being released. Some locks pick best with little tension dialed in, some require more."