Originally Posted by custom2
If anyone has any more info to share, please do.
It's not the hammer movement that you should be concerned with. It's sear movement. If the sear can't move, neither can the hammer. The thumb safety doesn't block the hammer. It blocks the sear.
Watching to see if the hammer moves is difficult without a dial indicator...and it depends on which direction it moves as to whether the gun is deemed safe or unsafe. 1911 hammers with ordnance-spec hooks will move backward a couple thousandths of an inch before the hammer falls due to the undersquare cut. Also...ordnance-spec hammer hooks are long enough to allow .005 inch of sear movement and still pass the serviceability test because the undersquare hook geometry tends to pull the sear back into engagement rather than push it out if the sear moves. If they've been squared and shortened during a trigger job...only zero sear movement is acceptable.
To check for sear movement:
Cock the hammer and engage the safety. Pull the trigger firmly and release.
Place the safety in the OFF SAFE position and slowly overcock the hammer past full cock, being careful not to let it contact the grip safety. With your ear close to the side of the pistol...listen carefully for a light "click." If you hear that click...the thumb safety isn't blocking the sear properly. The click is the sound of the sear resetting to the bottom of the hammer hooks.
Test the grip safety in the same way...this time with the thumb safety in the OFF SAFE position. Grasp the pistol in such a way as to avoid depressing the grip safety...pull the trigger and release...overcock the hammer and listen for the click. If you hear it...the grip safey isn't blocking the trigger properly.