View Full Version : Colt Python cylinder over rotating

July 15, 2005, 08:38 AM
When cycling DA slow and deliberate, timing seems fine. When DA is cycled as fast as possible, cylinder over rotates past the bolt. I did this while dry firing and of course not done this with live ammo.

Any insight would be much appreciated.

James K
July 15, 2005, 09:56 AM
This can sometimes be caused by dirt or old oil in the action. My preference for this sort of cleaning is G96 Gun Treatment, but any good penetrant-lubricant can be used (avoid WD-40; it will gum up). Remove the grips, cock the hammer and spray the penetrant down into the mechanism in front of the hammer, and in front of the trigger. Really soak things, then let the gun drain, work the gun, then do the spray routine again.

If the problem is persistent, then here is my advice, which you may choose to disregard: Unless you are a competent gunsmith, with special knowledge of those Colts, do not attempt to repair the gun yourself. Your best choice is to call Colt and describe the problem. They will either tell you to return the gun to them and most likely pay the shipping, or have you contact an authorized repair station. A good second choice would be Cylinder and Slide (www.cylinder-slide.com) but I understand they have a significant backlog.


July 15, 2005, 11:52 AM
Here's some additional information.
The condition is called "cylinder throwby." It can be caused by a hesitant or jerky trigger pull.
If it still occurs when you pull the trigger smoothly and evenly, with no sudden jerks at the beginning, then the revolver's timing is likely off.
And as Jim said, that's not a job for a kitchen table tinkerer (like myself).

Dave Sample
July 15, 2005, 01:19 PM
Ditto what Jim said.

July 15, 2005, 01:44 PM
Here's a repost of my instructions on checking the old Colt revolver action's timing.

In your case, pay special attention to the section on bolt drop timing. This describes WHERE the bolt should drop back onto the cylinder:

To check Colt timing:

Open the cylinder and look at the small "lug" in 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 THE INSTANT the hammer begins to move.
There MUST be NO (ZERO) hammer movement possible 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".
There should be no hesitation, and no amount of "creeping" back out.

Close the cylinder.
Use your left thumb or fore finger to again cock the hammer, closely watching the cylinder bolt as you SLOWLY cock the hammer.

As the hammer comes back, the bolt will retract away from the cylinder.

The bolt MUST retract far enough 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.
This often appears as metal "pulled out" of the lock notches, with rounded off and burred notches.

Continue to cock the hammer, laying your right index finger on the cylinder just enough to prevent "free wheeling". DO NOT press with any force, since this can cause a false "reading".

Watch for the bolt to drop back onto the cylinder. WHERE the bolt drops is CRITICAL.

The bolt MUST drop onto the leade or ramp in front of the actual cylinder notch.
If the bolt drops too soon, (in front of the notch ramp), it will mar the finish of the cylinder.

The bolt SHOULD drop into the MIDDLE 1/3rd section of the ramp.

If the bolt drops late, (farther toward the actual locking notch) the revolver may display "cylinder throw-by".
In this condition, during double action shooting the cylinder may rotate PAST the locking notch, and fire in an unlocked condition.

It's the nature of the Colt action, that a hesitant or jerky trigger pull by the user can induce throw-by in even a properly tuned Colt.
The Colt trigger should be pulled with a smooth, even pull, with no hesitation.

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 the hammer reaches full cock.

The most common Colt mis-time situation is the hammer cocks before the bolt drops into the lock notch. (Hammer is cocked, but cylinder isn't locked).

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.

In my experience, most Colt's leave the factory with the bolt dropping a little late into the leade, but usually wear in to correct timing.

If the bolt drops onto the cylinder early, no real problem, but there will be extra finish wear.

If the bolt drops late (closer to 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.

Each of these checks should be done on EACH chamber. All of these checks are better done individually. In other words, do the bolt retraction check on all six chambers, then do the bolt drop test, and so on.

A properly tuned Colt will:
Have a smoothly functioning bolt with no sticky or hesitant movement.

Unlock before the cylinder begins to turn.

The bolt will drop onto the middle 1/3rd of the ramp.

The bolt will drop into the lock notch before the hammer reaches full cock.

Have a smooth trigger pull, which does "stack" or get progressively heavier.

If anything is wrong, I strongly suggest sending your Python in to Colt for repair.
DO NOT trust any local gunsmiths. Few are qualified to work on the old Colt action, and usually do more damage than good.

James K
July 20, 2005, 09:20 PM
In my experience, the most common cause of throwby in a Colt DA is the trigger pull, either what Dfariswheel calls a "catch" or "hard spot", or the way the trigger is pulled. Here is what happens. The cylinder bolt (cylinder stop) is retracted from the stop notch in the cylinder. At this point, the cylinder is free to move clockwise (it can't move backward; the hand won't let it). Normally, the hand then pushes the cylinder around until the bolt drops and stops cylinder rotation.

But, if the cylinder is given a rapid "kick" by the hand and turns freely enough, its own inertia can cause it to move out of contact with the hand, and put the next notch beyond the cylinder stop before the stop is released to re-engage the cylinder. Normally, there is enough friction in the cylinder arbor and cylinder, plus the hand, to prevent this from happening. But some gun owners and gunsmiths feel that a cylinder that "spins forever" when out of the frame is ideal, and that is not necessarily true.

In addition, the amount of cylinder inertia is influenced by the number of cartridges fired. Since empty rounds will rotate toward the bottom of the cylinder, the heavier loaded rounds at the top can increase the inertia and the possibility of throw by increases.

So, why doesn't the same thing happen with an S&W? Because the S&W cylinder stop drops at about the halfway point between stop notches. That makes the distinctive "line" on an S&W cylinder, but there is a reason for it, and it is of no concern. But the Colt bolt spring is much stronger than that of the S&W, so if the bolt is dropped too soon, it will not just make a line in the bluing, it will make a dent and an actual groove in the cylinder, something Colt did not want to happen. So they lengthened the lead, and timed the gun to drop the bolt in the lead rather than on the cylinder. Naturally, Colt salesmen made a virtue of necessity and emphasized that Colts did not make that "ugly" line on the cylinder.