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Discussion Starter · #1 ·
Hello Guys (and Gals),

I'm new to the forum and have a question as follows:

I recently purchased an additional cylinder for my Colt
Diamondback .22 and very carefully rechambered it for .22 WMR (.22
Mag). The headspacing is exactly the same on all chambers and just
sufficient to reliably clear the frame when the cylinder rotates. The
problem is some cartridges do not fire. Inspecting the rims of
misfired cartridges clearly indicates the hammer/firing pin is not
hitting the rims with sufficient force to reliably ignite the
primers. So I have some questions. 1) Are the rims of 22 Mag thicker
or harder than standard .22 rimfire? 2) If so, is there a preferred
solution to this problem such as replacing the flat v-shaped hammer
spring or reshaping the hammer tip? 3) Are there stronger hammer
springs available? 4) I assume installing a heavier spring will
change the trigger pull, which is just about perfect now.

Wayne
 

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Without actually seeing the gun, I can't give a definite answer, but here's some things to check:

Something wrong with the re-chamber job.
Unless you're experienced at this, things can go wrong and cause problems with mis-fires.

Mis-fit cylinder.
Revolver cylinders ARE NOT "drop-in" They ALL need carefully fitting by experienced technicians. Few if any cylinders can just be installed with no fitting or adjusting.
Along with the cylinder, the ejector is also fitted in conjunction with the cylinder.
In almost ALL cases, the original ejector will NOT work properly with the new cylinder.
When cylinders are replaced, the cylinder and ejector are fitted AS A UNIT.

Firing pin protrusion.
The .22LR Diamondback specs are:
Minimum .030", Maximum .035".
You'll have to either buy or make a firing pin gage. This measures the protrusion of the firing pin protruding from the breech face.

Cylinder end shake.
Excess end-shake can cause misfires.
To measure: push the cylinder forward and use feeler gages to gage the barrel/cylinder gap.
Then push the cylinder to the rear and gage again.
Subtract one from the other, and that's amount of end-shake.
The spec is: The maximum allowed is .003"
If the cylinder has excess end-shake, this is a FACTORY REPAIR ONLY, or one of the few non-factory services that have the special hydraulic tooling used to stretch the cylinder collar.

Head-space for the .22LR Diamondback is:
Minimum .043", Maximum .048".

Weak or altered mainspring.
This is the most common cause of mis-fires in the Colt revolver.
The best course of action if the spring is out of spec is to replace it.
The spring is judged by weight of trigger pull.
The specs for a .22LR Diamondback are:
Single action: Minimum 3.0 pounds, Maximum 5.0 lbs.
Double Action Maximum 14 lbs.
Honestly, if your Diamondback's trigger is "about perfect" the mainspring has probably been altered by bending, and the spring is too weak to pop the primer.
Most people unused to the Colt action think the Colt stacking trigger is too heavy, and their first action is to bend the spring.

Miss-shaped or altered firing pin tip.
Check the condition of the firing pin to a known factory-new firing pin. Any signs of wear or alteration are cause for replacement.

Loose firing pin.
The .22LR pin should be solidly in place with NO movement possible.

Action problems that are causing the hammer to have it's free movement obstructed.
This can be anything from a safety link catching on the hammer to the double action strut hitting the trigger shelf, to a bent or damaged firing pin striking the frame, to a damaged/loose recoil plate.

Things NOT to do:
Do not alter a factory condition firing pin.
Reshaping the tip or increasing protrusion beyond factory specs is WRONG and will cause other problems.

Do not attempt to correct excess cylinder end-shake yourself.
This is nothing you can do without highly specialized hydraulic tooling. Attempting to do so will only destroy the cylinder.
Colt's are DIFFERENT. Unlike other brands, you cannot use washers or stretching of the crane to correct end-shake.

If everything checks out 100% in spec, you may have to bite the bullet and increase the mainspring weight.
You do this by bending the upper leg of the spring.
No heavier springs were ever made.
 

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There's your gunsmith (dfariswheel) talking, I would listen to him.
 

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Discussion Starter · #5 ·
Everyone, thanks for your comments.

Mr. dfariswheel,
I sure appreciated your very detailed comments and information. I checked the revolver specs with the new cylinder, against those you provided and here's what I found.
Firing Pin protrusion: .033"
Cylinder end shake .016"-.013" = .003"
Headspace with the new WMR cylinder is .052" (+/- .001"), which is what I rechambered it to because the rim of a 22 mag is approximately .006" thicker than a typical standard .22 rimfire. Headspace with the original cylinder is .046"

So I then measured the trigger pull with a RCBS Premium trigger pull scale. Single-action measured right at 2.5 lbs. I removed the side plate and the mainspring. Bent the mainspring as you suggested a couple of times until the pull measured approximately 3.5 lbs. Test fired the revolver with 50 rounds of CCI WMR ammo with no misfires. And I can visually see the difference in the firing pin indentions on the rim.

By the way, the new cylinder came with a new ejector, which was fitted in conjunction with the new cylinder. After rechambering, I also check the timing of the new cylinder and it was just about perfect. In this case the new cylinder was a drop-in with no modification required. Thanks again for your help.

Majic,
Prior to rechambering I checked the difference in bullet diameters. The CCI 22Mag ammo I have is .0015” larger than the standard .22 ammo, which I did not feel was enough to worry about. In reality the 22 Mag cylinder and ammo results in better accuracy than the original cylinder with standard .22 ammo.

The total conversion cost me $75 and some time. I located the new cylinder and ejector for $75 on a gun auction site. The cost of the .22 Mag finishing reamer was a wash since I purchased it for $50 and resold it for $50 afterwards. So, with the misfire problem fixed, I’m a happy camper. By the way, if anyone else is considering this conversion, I found there are at least two different cylinders for Diamondbacks, depending on the year of manufacturer/version.

Regards,
Wayne
 

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Discussion Starter · #6 ·
Thought I'd mention one other item about the conversion that likely applies to other colt models also. With the ejector installed the new cylinder was 0.0025" longer than the original cylinder, resulting in reduced (almost no) end-shake. The result was the revolver functioned fine until some unburned powder residue managed to find its way under the ejector (between cylinder and ejector). It was enough to keep the ejector from seating all the way down and locked up the cylinder from rotating. The solution was to remove 0.0025" from the front of the cylinder collar leaving .003" of cylinder end-shake. Works great now. I put over a hundred rounds through it since then with no problems. Just another reason why you should not expect one of these well-made colts to function if you drop it in the dirt.

Wayne
 

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Most revolvers are sensitive to dirt and grit under the ejector, and sometimes the grit gets embedded in the metal when the gun is fired.

The usual symptom is the cylinder binds, often on one or two chambers.
Since the embedded grit can be tiny and hard to see, a good scrubbing with a toothbrush is often needed to get it out.

One way to help prevent this, is to hold the revolver with the muzzle straight up, and vigorously operate the ejector to throw the empty cases and the accompanying dirt and burned powder well clear.
Holding the revolver in the usual more horizontal position allows dirt to drop behind the ejector, along with getting a case caught also.
 

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Discussion Starter · #8 ·
dfariswheel,
This was the 1st for me. I've put many hundreds of rounds each through my Python, Anaconda, and the Diamondback without a similar problem. Although I'm partial to Colt double-action revolvers, for this reason alone, I'd probably go with a single action if selecting a large caliber revolver for protection in bear country. One less reliability/functioning concern to worry about.
Wayne
 

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dfw has given a very detailed discussion of possible causes for the ignition problem. I will suggest another.

Your gun began life as a .22LR, which has a smaller diameter rim than a .22WMR. Therefore, when the .22LR firing pin strikes the larger .22WMR rim, it hits the larger cartridge head too far in from the rim edge to effect reliable ignition. Increasing the main spring tension might add enough force to the hammer to improve ignition on the larger rim.

I am always amazed when someone tries to send a .224" jacketed bullet down a .222" hole. Seems like a bad idea to me.
 

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Discussion Starter · #10 ·
JC,
No question that the diameter of the rims are different. The radius of the WMR is approximately .007" larger. I also check the firing pin imprints of a Ruger Single Six convertible revolver. I doubt the rim diameter is a significant factor. The Ruger firing pin hits well within the rim of both cartridges. For both cartridges the Diamondback firing pin actually strikes further out. I don't know for a fact but I believe the WMR cases are made of thicker brass, requiring more force to crimp the edge. In any case, bending the hammer spring did the trick.

As to you comment about the different bullet diameters, it doesn't seem to be a problem. As you likely know cast bullet shooters typically shoot hard-cast bullets around 0.001" to 0.002" larger than the groove diameter. Prior to making the conversion I did measure the Diamondback groove diameter by slugging the bore, and also firing a very low velocity WMR cartridge and catching the bullet . Both measured 0.223". The standard .22 ammo I have measures 0.223" diameter and the 22WMR is 0.224". Also, the WMR bullet does not seem to be jacketed. I may be wrong but I believe they are plated, which results in a softer bullet than jacketed ammo. As I noted earlier, I get better accuracy with the WMR ammo than several brands of standard 22 ammo. And certainly the forcing cone is significantly larger than the WMR bullet, so there is no bullet-shaving problem. The WMR bullet seems like a better fit, which may be one reason it results in better accuracy.

Wayne
 

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The magnum bullets are jacketed not plated therefore much harder than the smaller "lr" bullet. That's why I cautioned about the bore being undersized for the magnum load.
 

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Discussion Starter · #12 ·
Majic,

You are likely reading the advertisement on the ammo box. As far as I know all 22WMR ammo use plated bullets. The CCI Maxi-mag HP 22 WMR bullets I use does say jacketed hollow point on the lid, but they are definitely plated bullets. The manufacturers are using the term “jacketed” very loosely. These bullets are not made the way conventional jacketed bullets are manufactured. The outer layer of copper or brass is deposited in a plating bath. This leaves a thin coating, not the thicker jacket of a true jacketed bullet.

You know what they say about assumptions, so when I saw your response I called CCI to confirm my understanding before responding. The guy that answered confirmed, that although the box says “jacketed hollow point”, the outer thin layer is created using a plating process. This leaves the bullet much softer than a true jacketed bullet. Of course, a very thick layer, equivalent to a typical jacket, can be created using this process, but the CCI technician assured me the layer on their 22WMR ammo is quite thin. It’s just enough to reduce bore leading. Just squeeze one with pliers or cut one in half with a wire cutter pliers and you’ll realize how soft the bullet is.

Being an ex-marketing guy I can appreciate the desire by the bullet manufacturers to enhance their ammo sales using catchy terms. Saying the bullets are "Jacketed Hollow Points" has a better ring than "Plated Hollow Points". But in this case they are taking liberties with the terminology. By the way, if you pull one of the .22WMR bullets and look at it closely, you will note they are completely coated, which is technically possible but more costly with jacketed bullets. The jacket is a separate component of jacketed bullets. The lead core must be somehow inserted prior to compression, which usually leaves tell tail signs. Most jacketed bullets have an opening in the base or nose. You hafta have an opening someplace to insert the core. The jacket for full metal jacketed bullets require an additional step or two (normally referred to as “pointing”).

Wayne
 

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I cast bullets and use all kinds of scrap lead. A lot of it comes from bullets I scrounge out the berms at the range. I can't tell you the number of .22mag bullets I dug out the pistol berm and melted down. The lead melts and the jacket floats to the top to be skimmed off. I also understand swaging and several times have considered getting equipment from Corbin and set up to to make swaged lead and jacketed bullets. So this is not an assumption nor anything I have read off any package. CCI can tell you anything they want.
 

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Discussion Starter · #14 ·
Hello Mr. Majic,

I went to some extent to make sure my previous response to your comment was cordial and factural. But I see you have a problem with someone disagreeing with you and supplying facts from the manufacturer to support their position. By the way, if a copper or brass plated bullet is melted there will be a layer of copper or brass left after the lead is melted out, just like a jacketed bullet. But the layer is much thiner because it was plated on. I guess the bottom line is you can choose to believe or not to believe, regardless of the facts. But what would CCI know, and why would CCI lie? They only sell more WMR ammo than anyone else. Call them yourself. From my point of view the subject is closed and not worth spending any more time on
Wayne
 

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Discussion Starter · #15 ·
Majic,
Based on the "tone" of your response I wondered what "set you off" Possibly you misunderstood my previous posting. So I just reread my long-winded post about plated bullets. My comment about assumptions was not intended to imply you were making one. I meant that I did not want to make any, which is why I called CCI to get the facts.

Wayne
 

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I was not set off or upset. I was just saying what I had personally witnessed many times. Also a bullet jacket does not melt at the temperature you melt lead. The lead simply melts out of the jacket and an empty jacketed hull is left that floats. You just pick it out of the mix (I use a set of tongs to pick out jackets and wheelweight clips). The plating on bullets melts and you have a discoloration floating on the mix. When you flux the plating material and dirt clumps together and you scoop it off the top.
We just have a disagreement. You have one set of facts and I have another, but it's not worth anyone getting upset over so as you said the subject is closed.
 
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