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Discussion Starter #1
I have a 1968 Colt Detective Special suffering from light primer strikes. After some research, I determined it might be the mainspring having been weakened, so I bought a new old stock spring and had a gunsmith swap it out for the old mainspring in the gun. After I went to pick it up, they told me the old spring did appear to be modified and that the gun was shooting perfectly fine now. Well, yesterday I was finally able to shoot it for the first time since having them fix it, and it is immediately having the same issues. I can't get through 6 rounds without a light primer strike. I will likely give them a call back, obviously, but I supplied the part and they did exactly what I paid them to do, which was swap out the part. So, I don't want to just send it back to them and waste a bunch of additional money for them to experiment what the problem is, unless that's the best coarse of action. I just don't get how they said it was shooting fine with ammo I gave them to test it with, but for me a couple weeks later it doesn't work right at all.

Does anyone have any ideas of what else the problem could be if not the mainspring? The firing pin looks fine, and I don't know what else to think. I could physically tell that it gained several lbs of pressure on the trigger pull after the new spring went in, so I was sure that would fix the problem, but apparently not.
 

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Back in the 70s on the range we would witness recruits "double clutch" a revolver. A weak hand can cause the revolver to not fully cycle resulting in a weak or skipped hammer strike. The trigger is not pulled fully to the rear. Let someone else shoot the gun in double and single action and see if it occurs again. I assume the gunsmith fired it without issue.
 

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Discussion Starter #3
Thanks for the reply, Hootch. What the gunsmith told me was that it fired without issue. I won't be able to have someone else test fire it too soon, but if I can't find any other solutions, I'll definitely try that. It's possible I'm guilty of the double clutch. I'm a relatively new shooter, so it could be that I'm weak in the hand and not giving it enough strength. How much of a difference does that make though? I would imagine that regardless of how hard you pull the trigger, it releases the hammer at the same point on drawback resulting in the same amount lbs of pressure each shot, but I could be mistaken.
 

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It could be that the new spring was also defective and weak.

Another possible cause is a short firing pin.
There's a special gage that's used to measure firing pin protrusion but there are other ways of doing it.

The firing pin is measured by opening the cylinder, holding the cylinder latch to the rear and pulling the trigger.
Hold the trigger back so the hammer remains in the fully forward position.
Measure how much of the firing pin is sticking through the firing pin hole in the frame.

The specs for the Colt "D" frame .38's are......
Minimum.....042"
Maximum....056"

One other possibility is excess cylinder end shake.
Cylinder end shake is back and forth movement of the closed cylinder in the frame.
If the cylinder has excess end shake the cylinder can move forward in the frame and away from the firing pin, giving insufficient firing pin force.

To measure end shake use a cheap auto store feeler gage.
Push the cylinder forward and hold it forward while you use the feeler set to gage the gap between the rear of the barrel and the front of the cylinder.
Then push the cylinder to the rear and hold it there as you gage the barrel-cylinder gap again.
Subtract one measurement from the other and that's how much end shake is present.
(When pushed to the rear this is also the actual barrel-cylinder gap. The gap should be between 0.004" to 0.008" with 0.005" being about perfect).

Colt specs for end shake are very strict.....NO MORE then 0.003" can be allowed.
If there's more, the gun will possibly have miss-fire problems, and it will batter itself to death from the cylinder hammering back and forth as it's fired.
Excess end shake must be repaired and that means sending the gun to one of two pistolsmiths who can repair it.

The Colt cylinder design is different than any other brand. Unlike S&W and most others, you CANNOT put washers into the cylinder assemble. Doing so will destroy the cylinder when it's fired.
Repair requires a special hydraulic tool to stretch the collar on the front of the cylinder.
That collar is machined in one piece with the cylinder.

Pistolsmiths who are able to repair Colt cylinder end shake are....
Frank Glenn......

Frank Glenn-Glenn Custom Complete Gunsmithing Service Glendale AZ

Spartan Firearms.....

https://www.facebook.com/spartanfirearmcompany/

Both are Master pistolsmiths and members here on the forum..

DO NOT trust anyone else to do an end shake repair to a Colt. Virtually no one other then Colt ever had the special machine and there's really no other practical way to repair this.

As above try having someone else fire the gun for you to see if they too have miss-fire problems.
Next, try shooting it yourself with a firm grip and making sure to pull the trigger fully.
This does not mean jerking the trigger hard, it just means to make sure you pull the trigger all the way.

There is a method of insuring the gun itself is operating correctly and that's to slowly pull the trigger in double action.
If pulled slowly the hammer will drop without the added force of the hammer moving back beyond the drop-off point.
If it miss-fires when fired with a slow DA pull, the gun needs service to find and fix the problem.
 

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Discussion Starter #6
Factory ammo, plus have tried a few different brands. Some are better than others, but the issue still seems to exist beyond a single type.

And thanks a lot for the comprehensive answer, dfariswheel! Definitely a lot to chew on, so I appreciate it. I will have to try shooting it again with the slow method you described to make sure it's not just me, along with someone else trying it. The other two suggestions will take a little more effort to measure, but it gives a good direction to look in. Once I get a chance, I'll see if I can figure if the firing pin depth is long enough or if the cylinder is shaking too greatly.

Thanks for the help. Any other thoughts are welcome too if someone can think of something that hasn't been suggested.
 

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Was it a new spring or possibly a used spring? If a repop spring they're often higher tension giving increased trigger pull effort. There also used to be springs on the market by "Bullseye" and can sometimes found NOS...they are lighter tension than factory.

Also...does the problem happen in both singe-action and double-action shooting? If it shoots fine in single-action shooting and the light hits only occur in double-action it's probably the leaf spring.

Hope you get it diagnosed and sorted out quickly.
 

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Factory ammo, plus have tried a few different brands. Some are better than others, but the issue still seems to exist beyond a single type.

And thanks a lot for the comprehensive answer, dfariswheel! Definitely a lot to chew on, so I appreciate it. I will have to try shooting it again with the slow method you described to make sure it's not just me, along with someone else trying it. The other two suggestions will take a little more effort to measure, but it gives a good direction to look in. Once I get a chance, I'll see if I can figure if the firing pin depth is long enough or if the cylinder is shaking too greatly.

Thanks for the help. Any other thoughts are welcome too if someone can think of something that hasn't been suggested.
I asked about reloads for a couple of reasons, one of which is I've had misfires with some of our colt's but it seems that it was only with reloads.
The other reason is Speer states in their loading manual that the number one cause if misfires is primers not seated firmly.

But if your issue is with factory then the above doesn't apply.
 

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Discussion Starter #10
Was it a new spring or possibly a used spring? If a repop spring they're often higher tension giving increased trigger pull effort. There also used to be springs on the market by "Bullseye" and can sometimes found NOS...they are lighter tension than factory.

Also...does the problem happen in both singe-action and double-action shooting? If it shoots fine in single-action shooting and the light hits only occur in double-action it's probably the leaf spring.

Hope you get it diagnosed and sorted out quickly.
It's only ever happened once where it misfired in single action and basically has been exclusively double action when the light hit occurs. That's why I figured it needed a new mainspring. I'm not sure where the origins of the spring were, but the one I bought was off of eBay and listed as New Old Stock, so I imagined it should perform fine. As I stated in the original post, after the new spring was put in, the trigger gained a good few lbs of pressure The guy who did the work commented too that the old spring felt weak and he could visibly tell it was modified. With that being fixed, I'm confused why it still would be striking light.

Either way, thanks! I'm going to see if I can figure it out while I have a couple days off for thanksgiving. Will post back here with my findings.
 

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Discussion Starter #11
I asked about reloads for a couple of reasons, one of which is I've had misfires with some of our colt's but it seems that it was only with reloads.
The other reason is Speer states in their loading manual that the number one cause if misfires is primers not seated firmly.

But if your issue is with factory then the above doesn't apply.

Thanks for the input, Ken. Unfortunately with using factory ammo, that does rule out the problem simply being ammo. :l

If the range where you shoot has a range officer, ask the RO to go over your shooting and to check your gun. Most are there to help and are happy to assist a new shooter.
I've mostly shot at my friend's property out in the sticks, but I likely will go to a range to make it easier to figure this out. I didn't know you could ask for an RO to assist you, so that's pretty cool, and I likely will as I'm sure they'll be much more knowledgeable than I. Thanks, Jesse.
 

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Spirit,
Did you pinpoint a cause yet?

A new to me Official Police (also with a visibly modified V spring and smooth/light DA) light strikes in DA maybe 1 out of 10 shots. I also suspected the spring but it's tuned so I'd love to learn it's something else. I'm going to go through Dfarris' excellent suggestions.
 

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Discussion Starter #13
Spirit,
Did you pinpoint a cause yet?

A new to me Official Police (also with a visibly modified V spring and smooth/light DA) light strikes in DA maybe 1 out of 10 shots. I also suspected the spring but it's tuned so I'd love to learn it's something else. I'm going to go through Dfarris' excellent suggestions.
If yours is only failing to ignite 1 out of 10, then you're already having better luck than I. As for pinpointing the cause, unfortunate news, I think it might be the spring. I haven't had a professional look it over, but when I test fired it some more and also fired another detective special the worked properly, I noticed the pull on my light primer striking gun was noticeably lighter than the correctly functioning one. Which is a bummer, because I just had the spring replaced, and it seems like I might have to again. With that being said, how hard is it to replace the spring yourself rather than a gunsmith doing it? I don't really want to pay someone if I don't have to.

Your modified V spring very well might be the cause, but there's still a chance it could be something else. Hopefully something in Dfarris' reply helps! Regardless, that sounds like a nice Official Police you have there!
 

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Replacing a Colt "Vee" spring requires removing the grips, cylinder assembly, and the side plate.
This is not difficult but requires good gunsmith screwdriver bits and some care.

There are two ways to go, one is to follow the below instructions, the better is to buy the Jerry Kuhnhausen Shop Manual, Vol One, that covers everything in deep detail.

First....The book and screwdrivers......

https://www.brownells.com/gunsmith-tools-supplies/books-amp-videos/books/handgun-gunsmithing-books/colt-double-action-revolvers-shop-manual-volume-i-prod25720.aspx

Bits.
I recommend buying two thicknesses to cover variations in slot size. These are great driver bits and Brownell's will replace them FREE if you damage them. Just email them and they send a replacement.
I also recommend buying a "law enforcement" size handle. These smaller handles give far better control then bigger handles.
You can also usually find a shorter handle in a good hardware store.

Buy the following bits....

.150-2 and -3.
.180-2 and -3.
.210-2 and -3.

Dash 3 and up...

https://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/screwdrivers-sets/magna-tip-bits/magna-tip-super-set-bits-prod41568.aspx

Dash 2....

https://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/screwdrivers-sets/magna-tip-bits/magna-tip-thin-bits-prod425.aspx

Handles. I'd buy a magnetic and a clip retention law enforcement handle. In gun work you'll need both types...

https://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/screwdrivers-sets/magna-tip-handles/magna-tip-super-set-screwdriver-handles-prod400.aspx

Do it yourself spring replacement.....

First remove the grips.

Then the cylinder assembly.
On the right side of the revolver will be either the new style retention or the old type.
The old type is a "Figure-8" arrangement of a screw and interlocking stud.
Unscrew the screw and the stud is lifted out of the frame and the cylinder can be removed. It's usually not necessary to totally remove the assembly.
Open the cylinder and rotate it so a flute lines up with the lower-front part of the frame. Slide the cylinder and crane assembly out of the frame.

New type is a single large head screw on the right side of the frame.
This is actually a cap screw. Unscrew it and under it is a small spring and plunger. They may or may not come out with the cap screw.
Remove them, rotate the cylinder so a flute lines up with the lower frame and slide the cylinder and crane out.

NOTE: DO NOT attempt to disassemble the cylinder assembly. The old style require special tools, and it's always a risk to disassemble any version of cylinder assembly.

With the cylinder assembly out and the grips off, remove the two side plate screws. The screws are different lengths, make sure they go back in the correct hole later.

Hold the frame with a finger in front of the cylinder release to prevent it from popping out and loosing a tiny spring and plunger under it.
Holding the frame in one hand with a finger restraining the release, rap the side of the grip frame BELOW the side plate with a plastic screwdriver handle.
This will vibrate the plate loose.
Rap enough to loosen and lift the side plate but don't allow it to come all the way out, that may chatter mark the frame and plate.
Lift the plate off, making sure the cylinder release doesn't come out of the side plate.

Use a pair of smooth jaw pliers to squeeze the two "legs" of the Vee spring together while you unhook the top leg from the hammer stirrup.
Ease the spring out of the frame while keeping the spring compressed.

Use a stone to lightly round off and smooth the front edge of the Vee spring. This will prevent a sharp edge from catching on the rebound and giving a rough trigger pull.

Grip the new spring with padded pliers, making SURE to use some sort of padding to insure the spring isn't scratched. Any scratches may cause stress risers that can cause the spring to break later.
With the legs compressed, slip the spring into the frame and hook the hammer stirrup onto the hooks of the spring.
Push the spring in place and insure the hammer is hooked up with the spring and the lower leg is on the rebound lever.

Check the cylinder latch pin to insure it's facing out properly and in the small circular cut in the frame, and the cylinder hand is pressed in properly.
Holding the cylinder release in place insert the top of the side plate into the frame.
Sliding the cylinder release very slightly back and forth to insure it interlocks with the cylinder latch pin, press the side plate down into place.
If the side plate doesn't slip into the frame check the cylinder latch pin and the hand to insure they're in place correctly.
If the hand is out of place, lift the rebound slightly and push the hand down into place.

With the side plate fully in place, hold it down with a thumb and operate the trigger to insure it operates and the cylinder release pulls the cylinder locking pin back in the frame.

Install the screws, slip the cylinder assembly back in place and replace the retention.

This sounds more complicated then it really is, the only key is to not damage screw slots, dink up the frame or side plate, and insure the hand and cylinder latching pin are in place, and that everything works.

For a new spring, I'd recommend going to Jack First. They make correct factory spec new replacements.....

https://jack-first-gun-parts.myshopify.com/collections/colt-d-frame-revolvers/products/colt-d-mainspring
 

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Discussion Starter #15
Thanks a ton for that ridiculously comprehensive reply, dfariswheel. Especially listing parts/tools too. I don't have the time now with Christmas to get everything and try it myself, but I definitely appreciate your detailed and meticulous explanation of how to replace the 'vee' spring. I'm certainly going to keep it in hand for when I get around to doing so myself, and hopefully anyone else needing to know the same will stumble across your post. Cheers! And merry Christmas!
 
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