Detective Special Light Primer Strikes
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    Question Detective Special Light Primer Strikes

    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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    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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  5. #4
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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.
    Last edited by dfariswheel; 11-25-2019 at 12:13 PM.
    MarkInTx, Spirit and StenFreak like this.

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    Reloads or factory ammo?
    Ken
    "I like Colts and will die that way"

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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.

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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.
    Socialism is like a Jedi Mind Trick...it only works on the weak minded. SnidelyWhiplash
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    Quote Originally Posted by Spirit View Post
    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.
    Ken
    "I like Colts and will die that way"

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    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.

  11. #10
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    Quote Originally Posted by SnidelyWhiplash View Post
    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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