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How to CZ hammer coach spring strength reduction


Cahawbakid

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Title says it all, I have a set of replacement springs on the way from CZ ,I didn’t want to do anything until I had a spare set in hand.

 

The stock springs are a real Bear, I would like to reduce them around 25%. These are of course V Springs. I have a spring vise to remove and reinstall them. I’m unsure of the best approach to reducing the spring strength, what part of the spring to reduce. I know it will be the top leg, just unsure what to remove. 
 

Any input?

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Howdy Cahawba,

 

First it's good that you have replacements on the way and have a spring vise. Before you start removing metal or even dismount the springs, work the lock to see how the spring works. Is it scraping the lock plate? Once you see how the spring moves you can figure what part of the spring to (gently) pare down. I suspect that you will want to work on the long part of the spring that works on the tumbler (to which the hammer is attached). 

 

I think there is some debate about whether to reduce the width of the spring or the thickness. I don't know what the springs in you gun look like but my betting is to reduce the thickness carefully along the length of the spring. Go easy check the spring often. I have used fine files for this, always drawing the file lengthwise - never crosswise. When you are close to the reduction you want, start polishing the areas you have worked on. Be sure to remove all file marks so the spring has a nice polished appearance. Any scratches that remain can create a crack and failure later. One last proviso - DO NOT USE A DREMEL OR SIMILAR ROTARY TOOL FOR THIS WORK.

 

the foregoing has worked for me in the past (mostly on muzzleloder locks). I'm sure there are more skilled and knowledgeable folks here to offer good advise and correct anything I've said that is heretical.

 

Rev. Chase

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I used a drum sander on a Dremel tool to thin both legs of the springs on two different CZ Hammer Coach guns. Very successfully. Use long, full strokes the length of the spring. Do not allow the spring to get too hot to couch. I used an electronic trigger pull scale to test the spring strength before and during the grinding. You can use stones to polish the springs and remove scratches. One leg of the spring controls the hammer force and the other leg is for rebound. If the rebound leg is too strong it can cause light strikes and FTF so both legs have to be worked together.

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47 minutes ago, Cahawbakid said:

Did you grind the edge of the spring or the wide part of the spring?

I ground the wide part making the spring thinner. I polished the sides smooth but did not narrow them. It is important to keep the spring thickness uniform as possible so the entire spring does the work. A thin spot will do most of the flexing and fatigue early. If memory serves, those springs have some taper. Maintain that taper. 

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On 2/14/2024 at 6:23 PM, Lead Monger said:

I ground the wide part making the spring thinner. I polished the sides smooth but did not narrow them. It is important to keep the spring thickness uniform as possible so the entire spring does the work. A thin spot will do most of the flexing and fatigue early. If memory serves, those springs have some taper. Maintain that taper. 

I too did it this way,the Roger Rapid way. If you look at the ends ot the original springs they have a sharp tapper at the end, this allowing the hammer to drop close to the firing pin, no need for brass rings. Be sure to get the scratches out.

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  • 2 months later...

The idea of reducing springs without spares seemed like a bad idea. I called the CZ customer service number, spoke to a nice lady who said she would put springs in the mail no charge.

 

What came in the mail was more than expected, not just springs , two complete locks. I was shocked! 
 

Big ups to CZ for great service 

IMG_1273.jpeg

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I use the technique of working the width of a leaf spring narrower.   Hourglassing is what it is called, and it's much easier to control the strength of the spring.  

Taper both ends of the cut to make the narrow section.   Take some off, test the spring, when down close to desired weight, polish all scratches or grooves to remove stress raisers where spring steel can break.

 

good luck, GJ

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