View Full Version : Colt (Python & Old style) Trooper Timing

September 9, 1999, 02:35 PM
Howdy Folks,

I'm looking for some advice on a repair project I'm about to tackle.

I have a Colt Trooper with poor cylinder timing. It is a sixties vintage (I think), with the flat V mainspring, rather than the coiled mainspring. As the hammer is retracted, the bolt drops down just enough to allow the cylinder to start rotate. It pops back up as the cylinder has moved just enough so the bolt doesn't go back into the locking lug it just left. The bold continues to drag on the cylinder all the way to the next lug,
leaving that really "attractive" ring. I can live with the ring, but the next symptom has me worried.

If the hammer is retracted slowly, the clinder stops rotating just short of the bolt fully engaging the new locking lug. I have to manually bump the cylinder that last tiny bit before the bolt goes all the way home.
However if the hammer is retracted smartly, everything locks up fine. I'm guessing the extra speed of rotation gives the cylinder enough momentum to rotate fully.

The questions I have at this point are:

1) The assembly/disassembly manuals I have on hand, contain directions for Pythons and Officer Models. Is it safe to assume these are close enough to my Trooper, or do I need to get the Kuhnhausen manual for "I" frames?

2) Once I have it apart, if nothing is obviously broken, what do I look for? I'm guessing I check the bolt, hand, rebound lever, and ratchet for wear. I'm just not sure how to determine when the "wear" is too
much, or should I just start replacing all the usual suspects.

3) If I'm lucky enough to get to the point of identifying the offending parts, where do I get replacements? Brownells sells Python parts. Would these fit? Do I need to try and order them from Colt, or will I have to hit the used parts vendors?

4) I'm not a pro. I have had many pistols and a few revolvers (Dan Wessons and Rugers) detail stripped before, but never a Colt revolver. My skills could be described as a "hobbyist" level. Is this lockwork
more complex than I should be attempting?

I'm sorry this is so long, but once I got started with details, it was hard to know when to stop. Any insight or advice would be very much appreciated.



James K
September 9, 1999, 04:18 PM

Timing an old style Colt DA ranks right up there with a session in the Iron Maiden on a list of fun things to do.

My advice: send it back to Colt.

To answer some of your questions, your second paragraph describes normal behavior for Colt DAs. Even new, they rarely quite lock up when the cylinder is held or when they are cocked slowly. What really has you worried is really a non-problem.

The premature release of the bolt indicates that the back end of the bolt is slipping off the rebound lever cam, probably to the side rather than off the front as it should. If nothing is broken, that might be corrected by tapping the bolt to bend it a little more toward the rebound lever. It could also be caused by a rebound lever moving sideways if the pin is too small or worn. (Maybe a bad replacement pin; that you can check for just by removing the grips.)

Your other questions, I'll try to answer.

1. Colt always listed Python and parts separately, but AFAIK it is a J frame. Anyway, new J Frame parts are readily available from Gun Parts Corp. The Kuhnhausen book will certainly help.

2. If my guess is right about the bolt slipping, you may not find any wear. You will have to try to observe the action and see what is wrong.

3. See 1. above.

4. Yes. S&Ws are simple. See "My advice" above.


September 10, 1999, 10:41 AM
Thanks for the insights. I hadn't realized this was common on Colt revolvers. I'm going to the range after work today and I'll stop in the pro shop and check out a few Colts and see how mine compares.

I popped the "Gripper" grips off and checked
the rebound lever pin. It was slid to the right and flush with the left side of the frame. I'm not sure why it makes a difference, but this appears to be opposite what it should be. At least according to the photo in J.B. Wood's manual. I repositioned it, but the Grippers have a hole on both sides and probably aren't going to keep it in place. I'll have to dig out the originals and see how they work.

The other item that I noticed was the lower
leaf of the main spring isn't bearing against
the top of the rebound lever, except for the last half of the cocking stroke. I think the main spring has lost it's "zing".

I'm gonna pop the side plate off this weekend, when I have more time. See if there
is anything else I need to order when I get a new main spring.

Thanks again for your time...



4V50 Gary
September 10, 1999, 02:26 PM
Please confirm the interior of your Trooper is like that of the Python (except for the barrel and the fixed firing pin, the early Troopers were exactly like the Python). If so, then the bolt is dropping off the the rebound lever shelf too soon. I'll get back to you on my day off with the response (doing a double on Saturday and have committments tonight).

Vigilantibus et non dormientibus jura subveniunt

James K
September 10, 1999, 03:23 PM

The rebound lever pin should be flush with the frame on both sides and be tight enough not to slip out. Some smiths stake them.

On the mainspring, try bending it back to contact the rebound lever at the front. It may not hold, but will allow you to see if that is part of the problem. If the rebound lever is not going back into position, the cam might not be engaging properly at all, which could let the bolt drop too soon.


4V50 Gary
September 10, 1999, 09:08 PM
Response Part I. How the Colt I & D Frame works:

In the Double Action mode, as the trigger is pulled rearward, the hand is raised. The finger of the rebound lever rests on the pivot pin of the hand. So, as the hand rises and engages the ratchet of the cylinder, it carries the rebound lever upward and causes the tail of the bolt to pivot upwards. Resultingly, the bolt drops, disengaging it from the cylinder and allows the cylinder to be rotated by the hand. Concurrently, the safety lever is raised (by the trigger) causing the safety to slide downwards. The trigger nose now begins to engage the sear, allowing the hammer to start its rearward motion. When the hand rotates the the cylinder 1/2 to 2/3 of the point of indexing the next chamber, the bolt tail falls off the rebound lever shelf. The bolt is then forced upwards by the bolt spring, resulting in the bolt engaging the leading notch of the cylinder. The cylinder is then arrested from further rotation by the bolt which engages the cylinder notch. The trigger nose continues to raise the sear. When this happens, the hammer is forced forward by the pressure acting upon it from the rebound lever. The mainspring supplies the pressure for the rebound lever. The hammer falls on the frame mounted and spring loaded firing pin, which strikes the primer; thereby compressing the anvil in the primer. The crushing of the anvil grinds the primer compound to 300 degrees, thereby causing ignition. The flash travels through the primer hole into the chamber of the case, igniting the propellant. The gases formed by the propellant dislodges the bullet from the case. The bullet then begins its journey which will take it from the cylinder, past the barrel cylinder gap, through the forcing cone, down the barrel and eventually out of the muzzle.

As the trigger is released, the hand begins to lower and disengages itself from the cylinder ratchet. This permits the rebound lever finger to follow the hand downwards. As the rebound lever lowers, the shelf of the rebound lever forces the bolt tail raised. The trigger nose pushes the sear inward (towards the hammer) and an audible click can be hard as the trigger disengages the sear and allows the sear to return to its position of rest. The safety lever is lowered, allowing the safety to rise. The hammer is pulled away from the firing pin by the mainspring. The bolt tail now pops back onto the shelf of the rebound lever and another audible click is heard. The trigger is now returned to its position of rest by pressure from the finger of the rebound lever. The hammer returns to its position of rest by both the mainspring and a camming action from the rebound lever against the seat of the hammer.

When I return with Part II, I'll discuss timing the bolt. PS, it could also be your hand prematurely engaging the cylinder ratchet.

Vigilantibus et non dormientibus jura subveniunt

September 11, 1999, 11:39 AM
Wow Guys!!! I think I just got a priceless
bunch of info. Is this board great or what?!?

I've got the cylinder and yoke off, and have removed the side plate. The action looks just like the picture of a Python action in J.B. Wood's book.

First impressions are:

1) I've been oiling way too much. Break Free
everywhere, along with some gunk. Probably a
combo of oil, lint, powder fouling, and who knows what else.

2) None of the parts are broken. They all show wear, but it's more like they have been rubbing each other shiney. I guess this would be normal for a gun over 30 years old.
Kinda hard to tell if they are worn beyond proper tolerences without new parts to compare them to.

3) The mainspring and bolt spring are both a little wimpy. It takes almost no effort at all to compress them completely.

4) The bolt screw wasn't very tight. It started to unscrew as soon as I touched it with the screwdriver. I don't think it's been moving around, just not snugged down.
Should it be?

I think I'll start by ordering new springs and give it a good cleaning. I'm going to put it back together while I wait for the springs, while the process is still fresh in my mind. There sure is a lot of little parts
in there. I'm gaining a new apreciation for the folks with the patience to do this for a living!!!

BTW: Gary, I'm looking forward to your discription of bolt timing. I'm printing this stuff out, so I'll have a hard copy for
the future.



James K
September 11, 1999, 09:30 PM
Yes, the bolt screw should be snugged down. It is a two diameter screw so it can be tight without interfering with the bolt. That looseness could have been the cause of your problem. Snug the screw down and see it anything changes.

One more point to add to the fine piece by Gary. Those Colts have a double hand. When the hammer is coming back, the top engages one of the teeth on the ejector ratchet and starts the cylinder moving. As it turns, the lower notch on the hand engages the next ratchet tooth and continues the turning force on the cylinder. If the hand timing is not perfect, there can be a "catch" in the cylinder motion.

When the second ratchet tooth moves to the horizontal, the bolt drops into the cylinder notch. Look at this mechanism and you will see why there is a little play allowed in the cylinder/hand relationship. That is what caused your original question about the cylinder not locking when turned slowly.

If you are buying parts, a new hand might be a good idea, as yours might be worn too much.


[This message has been edited by Jim Keenan (edited September 11, 1999).]

4V50 Gary
September 12, 1999, 12:36 PM
Part II: Inner workings of the older Colts

Disclaimer. This information is provided for entertainment purposes only and neither its author nor The Firing Line assumes any liability for its use.

A word of caution on working on your own Colt I frame gun. Some guns have parts which performs a single function. On the Colt I or D or E frame guns, a part may perform numerous functions, all of which relates to timing. Changing one part may affect the timing of several other parts. This is especially true of the Rebound Lever. So, whereas one problem may be corrected, two or three others may have been created. Also, consider the cheapest alternative first which allows for restoration to status quo ante. Bending a part as a solution which you find doesn't work may be resolved by bending it back to its original shape. Removing metal may sometimes be remedied by lengthening by peening; the operative word is sometimes. Since Colt uses 4140 steel for its parts (on D, I and E frames), this allows for peening and shaping by filing/stoning to restore function. On a Colt, you should rarely need to replace parts. If a task appears too daunting, send it to a gunsmith.

So, with those words of advisory out of the way, let us begin by defining a common thread: definition. Unlike the cylinder stop of a S&W or Ruger revolver, the bolt on a Colt (D, I and E frame) is rather lengthy. We'll refer to the "cylinder stop" portion of the bolt as the bolt head and the opposite end which rests on the rebound lever shelf as the "tail". The actual tip of the tail will be referred to as the actuator.

With that, let's look at some ways to delay the bolt from popping up too early.

Recall from Part I how the hand raises the rebound lever and that that action causes the bolt to pivot downward and disengage from the cylinder notch. If you increase the time required for the rebound lever to rise, you delay the bolt's pop. This may be achieved by removing metal from the radius of the pivot pin of the hand. We're talking about removing metal from the top where the rebound lever finger rests on that pivot pin. The end result is that the rebound lever sits slightly lower, thereby taking more time to rise. Doing this should not affect the dropping of the bolt.

Another alternative is working on the bolt itself. As you recall, the bolt tail rests on the rebound lever shelf. If it's been bent previously such that it cants away from the rebound lever shelf. From a top view looking from the top of the gun towards the bottom of the grip, if the tail appears bent towards the solid side of the frame as opposed to the sideplate side, then the bolt tail and actuator sits more precariously on the rebound lever shelf, shortening the time it will rest on that shelf before dropping off (and allowing the bolt to pop up). The bolt may be placed in the vise and with only the tail exposed, grasp with a plier and tweak it (top view again) slightly to the left. This will increase the actuator's contact with the rebound lever shelf, thereby giving you a little more time.

Another thing we were taught was that the main spring could have been weakened, and that increasing spring tension could affect timing of the bolt.

I've also worked on a Colt Official Police. It has the same lockwork as the Python. It needed a new bolt and after it was fitted, the gun had more issues. The trigger was not returning because the bolt wasn't climbing back on the rebound lever shelf. I bent the rebound lever and then polished part of the shelf. I also polished to bolt tail and that only helped a little. The hand was polished to remove any scratches or burrs. My teacher diagnosed the problem back to the rebound lever. The rebound lever also pushes the hammer back, causing the firing pin to retract from the primer. It does it two ways. First is the mainspring which helps pull the hammer back. The second (and why it hung up) was that it pushes at the back bearing surface of the hammer, causing it to rotate back to its position of rest. The rebound lever had been worked over, removing too much metal from it thus not having the surface area to push on the hammer. The cheap quick fix (because no new rebound levers are to be had) was to file down the hammer block at 45 degrees, leaving only 1/2 of its contact surface to block the hammer. Now on Monday I have to lengthen the hand so it will rotate the cylinder earlier.

Finally, if these measures don't work, then fitting a new bolt may be in order. Alternatively, the rebound lever may have to be replaced (and may have been the culprit all the time). If it comes to either two, I'd recommend sending it to a gunsmith or back to Colt.

Notes on the hand: Like the Colt SAA, there are two steps in the hand. The top step initiates the rotation of the cylinder and the lower or second step completes the rotation. The top step should be inclined towards the center pin. If it doesn't, it can cause drag when the second step takes over the rotation. Also, the lower/second step should also be slightly inclined towards the center pin. The belly of the hand should not be so fat so as to push the first step away from the ratchet. With the side plate off, you can watch the hand move as it enters the hand window. It should begin from a retracted position and as it rises, then engage the ratchet. Near the hand's pivot pin you will notice that there is bevel for the finger of the rebound lever. If the two mate perfectly or close to perfect, then the finger will drag on the hand and could possibly prevent the trigger returning to position of rest when the trigger is release (sticky trigger). Polish the finger (not file) and you can gently file to alter the angle of that bevel on the hand.

Cylinder Disassembly: You need a special tool to grab onto the rachet. Brownell's sells it. Push the extractor to give full exposure to the ratchet. Then rotate it so you can unscrew the ratchet. Remove the ratchet. You now need another special tool to disassemble the cylinder screw.

Vigilantibus et non dormientibus jura subveniunt

September 12, 1999, 03:52 PM
Thanks a bunch guys.

Jim I think your sugestion that the loose bolt screw may have been causing problems is
right on the money. After reading and re-reading Gary's explination of bolt timing, it is clear how just a little lateral play on the bolt could have been allowing it to slip off the rebound lever too soon.

Add in the combination of weak springs, "gunk" slowing things down, and 30+ years of wear, and I guess it's no wonder the timing was off.

I put it all back together this morning, using the old springs. The bolt seems to be
staying down a little longer now. The tail doesn't slip off the rebound lever untill it is about half way between the locking lugs. I'll install the new springs when they show up. Hopefully they will help the bolt go into the lugs a little better.

If it neeeds more help beyond that, I think I'll let one of the local "smiths" have pleasure of keeping track of all those parts.

Even though I now understand a LOT more about Colts than I ever have, my own skills run more towards being a "parts swapper", rather than any real gunsmithing skills.

Thanks again guys....



October 31, 2000, 03:10 AM
Thanks Gary! lotsa reading to do on this...