Posted: 8/30/2015 9:32:29 AM EDT
In fitting new parts, fit the bolt first.
Note: The bolt spring that interacts with the hammer is sometimes relieved (filed so it is slightly trapezoid instead of rectangular) and if the bottom (the notch between the two legs) is square, then it could be slightly rounded with a needle file as this is a stress point.
The bolt head must fit each notch of the cylinder. If it must be narrowed, file it on the left and non-binding side. This may be done out of the frame. Next, check to make sure that the bolt head fits through its cylinder window (the opening in the frame that the bolt pops up and down out of). The bolt tail that interacts with the hammer must be nice and smooth and should correspond with the bevel of the hammer. As to the height to bolt must reach up, it should go as high as possible without bottoming out. That is, the bolt must be stopped by the frame and not the cylinder notch (this would create upward pressure against the cylinder).
In fitting the bolt to the hammer, there should be a .0001 to .0002" wink before the bolt contacts the hammer. That clearance determines the head start before the hammer contacts the bolt. Too much head start means the hand will try to rotate the cylinder before the bolt disengages the cylinder notch.
There is an arch in the bolt and this determines how long the bolt stays down. The longer it is, the longer it stays down. The shorter, the faster the bolt falls off the hammer.
Turning to the hand. Like the Python, the top of the hand begins the rotation and the second step of the hand completes it. The top of the hand should be as long as possible, but should not be so long as to begin the rotation before the bolt disengages the cylinder notch. The bolt should pop up before the second step of the hand completes the cylinder's rotation. The cylinder itself should be fully rotated to the next chamber before the second step finishes.
Trigger. The length of the trigger affects the timing of each notch. The trigger should push the hammer back slightly before the hammer falls off the sear. This makes for a neater trigger pull and is safe and secure. Trigger pull should be from four to 4 1/2 lbs. How far back into the hammer the trigger goes determines creep. Do not remedy it by reducing the hammer notch as it can cause the hammer notch to slam into the sear as it rotates forward. It is better to peg the trigger (drill the trigger & press in a peg to extend the back of the trigger and then file the peg to fit). If you find that there is not enough engagement between the sear part of the trigger and the hammer at full cock, you may relieve the back of the hammer slightly such that the sear part of the trigger sits further back.
Strongly suggest for anyone who wants to work on SAA or blackpowder Colts & Remingtons to take a NRA summer single action gunsmithing class. They're one week long and you learn a lifetime skill.
Great post and thanks for sharing your new knowledge!
Note on the hand: If it is too short, it can be peened to lengthen it. However, this may require that the second step be reduced (but you have to insert it and test it first).