This is a problem I experienced when developing a reduced trigger pull spring. What Tomac is talking about is not dry firing the weapon (letting the hammer fall), but simulating a fired condition with the bolt back and the trigger pulled. Release the bolt, then release the trigger, the disconnect resets the hammer caught by the sear when released. Using lubricants in the hammer group can create a sluggish trigger return in lower temperatures. This is another reason not to reduce the trigger pull too much if reliable operation is desired in low temperature conditions. Best thing for this is to keep the hammer pack relatively unlubricated and clean from excessive, temperature sensitive oils.
