Questions about newly acquired Colt Diamondback .38 4" barrel - Pistolsmith

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Old 01-26-2014, 10:09 AM   #1
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Questions about newly acquired Colt Diamondback .38 4" barrel

My Father recently came across a Colt Diamondback in .38 with 4" barrel and bought it. It has some bluing worn off in places but no rust. The pistol looks to have been fired a lot. One of my questions is about the firing pin. The firing pin has some vertical play in it or in other words it moves up and down and has some wear at its point. Is this normal? I found a diagram online and saw where the firing pin itself is pinned to the hammer. This could explain it but not sure if is should move or not.

Another issue we are concerned about is it seems to have some play in the cylinder when it is locked. We are worried it may shave some lead. How much play is normal?

Thanks for any help, I am new to Diamondbacks but not firearms and have been learning all I can and will be the first to admit not knowing a whole lot about these issues.


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Old 01-26-2014, 03:14 PM   #2
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Firing pin play = normal.

To test the cylinder play on THAT gun, cock the hammer back and while holding it back, hold the trigger back. It should be tight on THAT gun. If it isn't, you probably have issues.
Old 01-26-2014, 04:18 PM   #3
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As above the Colt double action, center fire revolvers with the firing pin on the hammer REQUIRE the firing pin to have up and down movement.
This is to allow the firing pin to align itself with the firing pin hole in the frame.
The firing pin should have minimal side to side movement.

As above, to test the older type Colt action, pull the trigger and hold it back. The cylinder should lock tightly with the Colt "Bank vault lock up".
If the cylinder has movement, the gun should be returned to Colt for repair.

To further check your new Colt, here's my instructions on how to check it for proper timing:

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, LIGHTLY laying your right index finger on the cylinder just enough to prevent "free wheeling".
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 “about” the middle 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 sudden jerks at the beginning.

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.
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 of the ramp.

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

Have a smooth trigger pull, which does "stack" or get heavier as the trigger is pulled.
Old 01-26-2014, 07:29 PM   #4
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Location: East Tennessee
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Thanks for the information and instructions. I will go over to my dads house tomorrow and check the diamondback to see if it has any issues. Thanks again.
Old 01-27-2014, 05:22 PM   #5
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Location: East Tennessee
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I checked the pistol out today and everything seems to be good. The cylinder locks up nice and tight with the hammer cocked and the trigger pulled. Thanks for the help.
Old 10-09-2014, 03:06 AM   #6
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cylinder lockup

"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."

What can be done to fix this problem if it persists?
What do you mean by 'usually wear in to correct timing'?
Do you mean that if I keep shooting with it regularly, then the problem will correct itself?
How many shots should that normally take?
Old 10-10-2014, 07:50 PM   #7
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The correction for "Cylinder fails to lock when slowly cocked" is to send the gun in to Colt or Frank Glenn in Arizona to have the "hand" that advances the cylinder either stretched or replaced.

If the hand has already been stretched, replacement is necessary since the hand will usually crack or break if it's tried again.
WARNING: The hand is not stretched how or where you'd normally think.

If the gun is still locking up when the trigger is pulled or the hammer is cocked normally, the gun is still safe to shoot AS LONG as it IS locking when the trigger is pulled.
Since it is out of time, whether to get it repaired now, or wait and possibly not be able to find a qualified technician is a risk.

If you smart, you won't take this it any local gunsmith no matter how good his reputation.
Almost no gunsmiths today really understand or are qualified to work on the old type Colt action, no matter what they say.
It's very common to take a Colt to a local and get it back with the original problem not corrected and with new problems caused by uneducated attempts to fix something he didn't understand even though he assured you he knew all about Colt's.

For that reason, if you're smart send it to Colt, or if you're not willing to wait until Colt can get to it, Frank Glenn is a well know Colt expert who's faster:

Colt's Manufacturing LLC

Frank Glenn-Glenn Custom Complete Gunsmithing Service Glendale AZ

Last, what I meant about "wearing in" I meant that the factory often timed revolvers so the locking bolt would drop a little too close to the locking notch, but as the gun was used it would "wear in" until the bolt was dropping right in the middle of the ramp in front of the notch.
This has nothing to do with the cylinder not locking up when slowly cocked, and further shooting will only make the locking problems get worse over time.

Last edited by dfariswheel; 10-10-2014 at 07:54 PM.
Old 10-18-2014, 03:55 AM   #8
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Join Date: Oct 2014
Location: Cedars
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Thanks for the detailed reply.
Unfortunately, I live outside the US and I frankly wouldn't trust anyone to repair or fix the problem.
Guess it's not really a problem. The gun shoots well in double action and the cylinder always locks when this is done with the trigger.
In single action the cylinder locks when cocking the hammer, if cocking the hammer is done relatively briskly.
If the hammer is cocked slowly then the bolt will not lock, staying just short of locking by about 0.5 mm or less.
However, the bolt always drops in the middle of the notch, whether cocking with trigger pull or when pulling the hammer back manually (as in single action). It's just that when the hammer is pulled back slowly the bolt doesn't reach the locking stage.
As I can't reach Colt, I guess I'll just have to live with the problem.
I purchased the gun recently, and in my opinion it was still brand new having never shot more that 5 to 20 shots. It's one of those guns that stayed in a drawer for a long time until the owner finally preferred to convert it to cash.
If there was a gun part I could order and install myself, that could be an option... Like change the hand (whatever that is???). But the gun was certainly never used by the previous owner enough to stretch anything on it!
Old 10-18-2014, 05:18 PM   #9
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Join Date: Jun 2001
Posts: 1,800
Critical Colt parts like hands are almost impossible to find these days. There are replica parts being made.

FITTING a new hand is nothing you really want to tackle unless you just have no choice.
The correct repair is to stretch the hand as I explained above.
The older Colt action is complicated and not at all intuitive, and critical working surfaces are tiny and not at all obvious.
What seems to be happening is not what's happening at all, which is why the older Colt's have the reputation of being "watchmaker's guns".

I recommend spending a few dollars and ordering the Jerry Kuhnhausen Shop Manual on the earlier Colt revolvers.
This was written as a training aid for new gunsmith students and goes into deep detail on all Colt pistolsmithing.
It's worth the money just so you can know if the gun is working correctly, even if you don't intend to work on it.

The manual does show how to stretch the hand the correct way.

Brownell's will ship overseas.

With that said, as long as the cylinder DOES lock up when the trigger is pulled, it's safe to shoot.
Treat it gently and it's likely you'll never have to have it repaired.

Last edited by dfariswheel; 10-18-2014 at 05:21 PM.
Old 10-19-2014, 03:36 AM   #10
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Join Date: Oct 2014
Location: Cedars
Posts: 4
Bless you, my man.
Your information has been enlightening and informative.
I just ordered the book from Brownells.
In the meantime, I've put about 300 shots through it and its working fine. Gonna keep treating it like a baby. Thanks a bunch...

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