In response to an emailed question, this is the procedure I use… There are quite a few out there, this is what I learned and copied down from an old time Colt guy.
To check Colt timing:
There are four separate actions that you need to do…
Locking bolt retraction and return-
Open the cylinder and note the small ‘bolt’ sticking out of the bottom of the cylinder window. This is the cylinder locking bolt. Cock the hammer, and watch as the bolt retracts into the frame and pops back out.
The bolt MUST begin to retract immediately as the hammer begins to move.
There must be ZERO hammer movement before the bolt starts to retract.
The bolt should retract smoothly with no hesitation until it’s fully retracted, then it must pop back out with a clean “snap”.
Note: The locking bolt should not hesitate, or creep coming back out.
Cylinder unlock-
Close the cylinder and cock the hammer, again watch the cylinder bolt as you slowly cock the hammer.
As the hammer comes back, the bolt will retract away from the cylinder.
Note: The locking bolt must retract to unlock the cylinder before the cylinder begins to rotate.
If the bolt is still slightly engaged with the cylinder lock notch, the cylinder will be attempting to turn while still partially locked. This produces a “catch” or “hard spot” in the trigger pull and will damage both the bolt and the cylinder lock notches.
Bottom line, the timing is off and needs to be adjusted by a qualified gunsmith.
Locking bolt release timing-
Continue to cock the hammer, put enough finger pressure to prevent free wheeling. Watch for the bolt to drop back onto the cylinder. The bolt must drop onto the leading edge of ramp in front of the actual cylinder notch. If the bolt drops too soon, it will mar the finish of the cylinder. TIMING AGAIN…
The bolt should drop into “about” the middle of the ramp.
If the bolt drops late, missing the lock the revolver may do what is called “cylinder throw-by”. In this condition, during double action shooting the cylinder may rotate PAST the locking notch, and fire in an unlocked condition.
Note: The Colt trigger should be pulled with a smooth, even pull, with no sudden jerks at any point.
Cylinder lockup.
Continue to pull the hammer back and both watch and listen for the bolt to drop into the cylinder lock notch. The bolt must drop into the actual lock notch before or just as the hammer reaches full cock.
Note: The most common Colt mis-time situation is the hammer cocks before the bolt drops into the lock notch. In this condition, with the hammer fully cocked, you can push the cylinder slightly, and you will hear the “CLICK” as the bolt drops into lock.
If the bolt drops onto the cylinder early, no real problem, but there will be extra finish wear. If the bolt drops late (close to or on the lock notch) the cylinder may “throw by” or rotate too far in double action and this can cause off-center primer hits and firing while unlocked. Lastly as each cylinder locks up, physically try to move the cylinder toward the muzzle then toward the hammer to check for cylinder ‘shake’ for each cylinder. This indicates there is no looseness in the center pin and everything is as tight as it should be.
You should do each of these checks on each chamber. While it takes a few minutes to do, it’s well worth the effort to know you have a fully functional and timed pistol!!!
Note: A properly timed Colt will have a smooth trigger pull, and will not “stack” or get heavier as the trigger is pulled.
A caution here too… Due to the timing critical to Colt operation, a hesitant or jerky trigger pull by the user can induce throw-by in even a properly tuned Colt…
And now I’ll stand by for the flack from the S&W users as how none of this is necessary on a S&W… And how ‘finicky’ Colts are…
FWIW, I finally sent one of my Pythons and a Diamondback out for a tune up after 20mumble years and probably 20,000 rounds and there were NO major problems with either one, so there…