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Discussion Starter #1
I recently acquired a model 66-2 that someone has obviously been doing some trigger work on. The single action is startling and the double action is very smooth and light. In single action mode I have no problems at all, and in slow double action I have no problems, however if I do quick double action taps I get a failure to fire 1-2 rounds per cylinder.
The primers on the rounds that did not fire show exceptionally light strikes. Sometimes I can hit them again and they will go but not always.
I ordered a set of reduced power rebound and hammer springs, and put the lowest power of the set in (which was a fair amount heavier than the ones that where in it) and saw no improvement in reliability. I am starting to question whether the firing pin is a tad on the short side?

any input?
 

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1st off, Welcome to the forum ! welcome01

Regarding your problem... by hammer spring do you mean the main spring, the leaf spring under the grips ? If thats to light you will get light strikes. The strain screw, the screw on the bottom of the front of the grip fame, is it tight ? is it the proper length ? a lot of kitchen table gunsmiths shorten this instead of using a lighter mainspring. The only other thing I can think of (off the top of my head) is endshake... that is front to back movement of the cylinder in the frame. Some is normal, to much will get you light primer strikes.

There is a lot of other more knowledgeable people on this forum who may chime in with some other ideas... but give those things a look... and get back to us.

If I had to guess... without seeing it in person, I'd go with a new strain screw.

Good luck kfjdrfirii
 

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Hi cutlass take off your grips, now back off the strain screw find a spent large pistol or rifle primer, take out the anvil and place the primer on the end of the strain screw. Re tighten strain screw, this trick has worked for me on many occasions.
 

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I always run full power main springs. It sure will pop any cap. In your case Federal primers/ammo may be the only ones to be reliable because of the reduced power main spring.
There are other things which will affect ignition. The strain screw must be in all the way and tight.
Make sure the gun (under the ejector) is clean and dry.
Check the endshake and keep it .003 or better.

I have put some notes in the FAQ, so if you have time check it out. ;)
 

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I can't speak to the spring issue but I had a model 65 that was acting the same way. It was endshake. A very quick and cheap fix for that.
 

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Discussion Starter #6
thanks for the welcome to the forum revorg!

Yes, by hammer spring I did mean the main spring. I ordered a "reduced power" spring from midway and installed it, it alone is substantially heavier than the one that was in there.

The strain screw is tight though I do not know if it is proper length or not, what is the length supposed to be?

as far as endshake, while I have not measured it I did drop the hammer and try to wobble the cylender, there was very little play. If I can put my hands on mt leaf feeler guage I will check it for an actual measurement.

I will take a look at the faq, thanks for all the info!
 

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I added another to the FAQ. I didn't notice I missed the test hammer spring notes...
Here's my way of testing the hammer spring...


Test Hammer Spring

First, make sure the hammer spring (main spring) is flat. Check this by removing it from the gun and laying it on the table. If it’s not flat, use a rubber mallet and tap it down.
This is how I test the main spring: Always keep the strain screw tight. Then you hang weights off the hammer until the proper poundage is reached.

You file the strain screw down to adjust the poundage to at least the minimum setting. Remember, the strain screw is always fully tightened, and the side plate is on when doing this work.
Gun empty! (for 22 revolvers, put fired cases in chambers.)
Dry fire gun and hold trigger fully to rear. (The muzzle is pointed straight up while you do this test).

Cock hammer with thumb, then hook a weight around the hammer (3 1/2 LB min weight for 357. 3 ¼ LB for 38 special) I hang the weight with a piece of string looped on the end of the hammer.
The hammer must not move rearward (further back under the weight) when the gun is lifted, while the weight is attached.
The factory has heavy triggers because they don't need any accidental discharges or any extra lawsuits. Also the guns have rough spots that the heavy springs cover up. The guys putting them together don't care if it's done right or not either.

Sometimes an extra long firing pin may help with poor ignition problems. But the spring must be right too.

A “home” gun smithing way of reducing trigger pull: if you don't want to file down the screw, then using blue locktite (thread locker) back off the strain screw until the gun misfires, then go back in 1/4 turn.
Some guys cut the main spring down by removing strips (long wise) to weaken it.


With my guns, I always run full power main springs but put reduced power rebound springs to help with the double action trigger pull. This is the best way of keeping ignition yet having a lighter pull. As long the trigger resets quickly, the rebound spring is the correct one for your application.
 

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Discussion Starter #8
I am still a little curious why I only have misfires on quick double action shots? If I only shot single action or slow creeping double action, I would never have detected the issue?
 

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Discussion Starter #9
BY The way, I saw this exact same issue on a 625 45acp that a buddy of mine had that also had a an obvious "trigger job"
 

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cutlass1972 said:
had a an obvious "trigger job"
It needs to be done correctly. Just swapping parts or springs may or may not work 100% of the time. Sometimes special ammunition must be used or misfires will occur. That's why I prefer full power main springs and reduced power rebound springs. There are other tricks to lighten the pull, but changing the rebound is often preferred when you need or want the gun to always work.

In addition to the springs being adjusted, trim a coil or two from the bolt spring. Then file the back side of the thumb release (bolt) around .04-.05 inch. What your trying to do is have the bolt retract further to the rear when the cylinder is closed. This will cause the cylinder to be "looser" because of the spring pressure. The less drag on the action will result in a lighter DA pull.
 

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Discussion Starter #11
OK, I am finally getting back to this. I replaced the hammer nose and it didn't seem to help.
I checked the endshake. It measures .0015 when I press the cylinder forward, and .011 when I pull the cylinder back so that is a difference of .0095. I think I am good here.

My next step is going to be to shim the strain screw as someon advised earlier adn see if the fixes it.
 

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Bingo!

You found your problem. End shake should be .001 or .002 thou and yours is pushing .010.

Get the end shake corrected and your misfires will be fixed too. kfjdrfirii

If you go bearings see the FAQ, I have repair notes on how to fix it.
 

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Discussion Starter #13
500, you are a godsend! thank you for sharing your wealth of knowledge!

I have a couple of questions though. If I read correctly about installing the endshake bearings, they go in front of the cylinder, can they not go behind the cylinder? If I put them in front of it, it will tighten up my endshake but also increase my air gap right?

also, I am not seeing your yoke squaring tool on midway's site, is there another name for it?
 

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your right about the cylinder gap but it won't make any appreciable difference and you will have a functioning gun again. I did the end shake fix on a K frame I have and it is now 100 percent reliable.
 

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Discussion Starter #16
I am just worried as my gap will be a bit on the wide side. Someone has either shot the hell out of this revolver or been shooing some really hot loads!

I am having trouble understanding why we need to use the yolk reamer? Is there a ridge on the yoke from the cylinder bearing on it for thousands of rounds that has to be "reamed" beyond so that the endshake bearings will slide onto the yoke?
 

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I am not sure what the tool is for. 500 will have to tell you that. In my case the bearing slid right on. An easy fix.
 

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quote "I am just worried as my gap will be a bit on the wide side. Someone has either shot the hell out of this revolver or been shooing some really hot loads!

I am having trouble understanding why we need to use the yolk reamer? Is there a ridge on the yoke from the cylinder bearing on it for thousands of rounds that has to be "reamed" beyond so that the endshake bearings will slide onto the yoke?" unquote

When shimming the yoke or stretching the yoke , the cylinder will move to the rear. This means the cylinder air gap will grow. Cylinder end shake must be as little as possible, so the gun won't bind up. This is normally .001-.002 for the best all around preformance.

In your case the firing pin is striking the primer, but the cylinder is absorbing some of the firing pin energy by pushing the cylinder forward. The main spring doesn't have any extra energy to overpower the cylinder absorbing some of the spring energy so this is why you have misfires.

The yoke must be square so you get the best possible repair, this is why you need the yoke facing tool. The insides of the yoke will have a ridge running around it's base, this needs to be cleaned up too (using a stone or a endmill etc). If both surfaces are square & flat, then you drop the desired amount of spacers inside the cylinder (with oil) then the repair will last for many many rounds.

The only way to fix the cylinder air gap is to turn the barrel, then recut the forcing cone to around .004 air gap. This job is for the factory who has the required tools and know how.
 
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