Today I did some test work for another shop on a S&W 645 that was in for a detail clean and strip and for a function test.  The owner complained of inconsistent primer strikes causing the gun to malfunction.  Upon further inspection it was determined that the mainspring had been trimmed to lighten the trigger.  This is one of the most common mistakes the home enthusiast makes.  When you start cutting coils from springs you run the risk of...