Colt's Diamondback .38 Misfires Question

OutAtTheEdge · Mar 9, 2025

Beautiful late winter day here in central Wisconsin, so I dragged myself off the couch and out to my shooting bench to see if I remember how to shoot. Was doing quite well with a half-dozen different .38 Specials and .45 ACPs, when I got to the lone dancing pony in my possession. I picked up this nice old Diamondback about 10-12 years ago. My justification, as I recall, was that my wife is a horse-fancier and, well, that was all I needed.

The Colt was shooting about as well as I can through a couple cylinders, all single action. Then I thought I'd run through a few rounds DA (which I apparently had never done before), and.....misfires. Light strikes, every single round, with very shallow primer indents. I popped the stocks off, and the mainspring doesn't look necessarily "bad", but as I've never done much fooling around with the non-S&W revolvers, I'm not sure how to tell.

The ammo in question is from a batch of handloaded wadcutters that have never given any trouble in any other gun, firing SA or DA. My strong suspicion is it simply needs a new mainspring, but before I invest in one, does anyone have any other thoughts?

Bullet Bob · Mar 9, 2025

This will be an unpopular reply, but my amateur advice is to leave it alone, and just shoot it in single-action. Everything in a traditional Colt revolver action affects everything else. If you can't live with it as is, I would send it to one of the places specializing in these fine old guns.

Of course you could do it yourself, and everything could work out fine. There aren't many absolutes in life.

BAM-BAM · Mar 9, 2025

Had the same problem with a .38 Diamond almost 30 years ago.

Use to be "Pittsburgh Handgun Headquarters" was a Colt Service Center. Closed down about 10/15 years ago

Don't know of any Colt Service Centers [Gunsmiths] still around.

SnidelyWhiplash · Mar 9, 2025

What you're experiencing is the classic signs of a ham-handed attempt at lightening the trigger by modifying the mainspring. While there is an accepted way to do it...far too many people that try do it wrong or go by the adage "if a little is good enough then more must be better" and ruin the mainspring.

Take the stocks off and look at the leaf-type mainspring. The upper leg should be straight. If it's got a hump in it then someone modified it incorrectly.

While you can try and bend it back to spec...at least to some degree...the best thing is to replace the mainspring with a known good one. It's not a difficult job at all but does require removing the side plate and parts can be jounced out of position.

Once that is done all should be right with your Diamondback.

OutAtTheEdge · Mar 9, 2025

SnidelyWhiplash said:
What you're experiencing is the classic signs of a ham-handed attempt at lightening the trigger by modifying the mainspring. While there is an accepted way to do it...far too many people that try do it wrong or go by the adage "if a little is good enough then more must be better" and ruin the mainspring.

Take the stocks off and look at the leaf-type mainspring. The upper leg should be straight. If it's got a hump in it then someone modified it incorrectly.

While you can try and bend it back to spec...at least to some degree...the best thing is to replace the mainspring with a known good one. It's not a difficult job at all but does require removing the side plate and parts can be jounced out of position.

Once that is done all should be right with your Diamondback.

Thanks. This is pretty much what I was thinking, I just wanted to get some confirmation.

Protocall_Design · Mar 9, 2025

Snidely Whiplash has the answer. If you try to get the spring back to original and it doesn't work, you would have to get a new one anyway.

stansdds · Mar 9, 2025

SnidelyWhiplash said:
What you're experiencing is the classic signs of a ham-handed attempt at lightening the trigger by modifying the mainspring. While there is an accepted way to do it...far too many people that try do it wrong or go by the adage "if a little is good enough then more must be better" and ruin the mainspring.

Take the stocks off and look at the leaf-type mainspring. The upper leg should be straight. If it's got a hump in it then someone modified it incorrectly.

While you can try and bend it back to spec...at least to some degree...the best thing is to replace the mainspring with a known good one. It's not a difficult job at all but does require removing the side plate and parts can be jounced out of position.

Once that is done all should be right with your Diamondback.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Excellent advice.

Ghostdriver · Mar 9, 2025

My Diamondback had the exact same problem. I think mine is a late 60's or early 70's. The short story is I put a new main spring in it and it seems fine now. The longer story is mine had a small area towards the top that was hogged out with a dremmel type tool to clear a pin in the action. Make sure you look for that because mine wouldn't work without it. As others said it's a pretty easy job but be careful of the spring for the cylinder latch doesn't fly out.

SnidelyWhiplash · Mar 9, 2025

The same thing can happen in a S&W when someone tries to back off the strain screw too much in an attempt to lighten the trigger pull. People all too often mistake wanting a lighter trigger pull when what they mean is they need a smoother trigger pull.

The two are not the same thing and one can have a much better and smoother trigger pull without it being lighter and potentially reducing reliability.

There are Bubbas everywhere and it doesn't matter is if it's a S&W, a Colt, a Ruger or any other make...no matter how the factories may try...they cannot truly Bubba-proof their products. There are tried and true genuine techniques to help a revolver or pistol's action but some are bound and determined to find a short cut and then blame the manufacturer.

OutAtTheEdge · Mar 9, 2025

SnidelyWhiplash said:
The same thing can happen in a S&W when someone tries to back off the strain screw too much in an attempt to lighten the trigger pull. People all too often mistake wanting a lighter trigger pull when what they mean is they need a smoother trigger pull.....

Ah yes, the poor man's trigger job.Had a customer, probably 30 years ago, came in and bought a brand new Smith revolver. A few days later he brings it in complaining of frequent misfires. One look showed the strain screw backed way out. I tightened it back up right there in front of him and told him that should fix it. He tried the trigger pull and said I'd just screwed up the trigger job he'd paid his buddy $20 for.

Colt's Diamondback .38 Misfires Question

OutAtTheEdge

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