66-1 transitional light firing pin strikes

ExRanger714

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Bought this one and at the range noticed it would misfire on at least one, and not always the same, chamber. Primers (CCI Blazer Brass and MagTech ammo) showed light almost centered strikes.

There was endshake but that cleaned up when I swapped sideplate screws. This did not solve the problem. Mainspring was screwed down tight.

Overall the gun looks ok. There are very minimal drag marks on the hammer like from a piece of grit on the side of the hammer. The firing pin channel is clean and not beaten up. Ditto the hammer face, frame and sideplate edges. There are no contact marks on the hammer to indicate it is anything but right.

Hammer nose firing pin moves freely and not marred by drag marks but it does look polished where is passes through the firing pin bushing.

Flash gap is .005 on all six when the cylinder is rotated and recoil shield/cylinder is .023 all the way around as cylinder is rotated so I'm thinking the cylinder is machined and installed squarely.

I borrowed a mainspring from a 28-2 and swapped and got 12 rounds of Federal to fire no problem. Firing pin impressions look deeper but I'm not set up to measure that. Impressions are still slightly eccentric.

Original mainspring looks odd with maybe signs of being bent or warped a little compared to another mainspring.

To see if it's really fixed will take time and cylinders of different ammo but if this ins't it what's next? If I left out a diagnostic exam please tell me what I missed.

Is .023 within normal limits for cylinder/recoil shield clearance? My 66 nd that runs fine ran out to .005 and .022 so it seems like it's on spec.

Thanks in advance and Regards. JD
 
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The rear gauge or headspace should measure .012-.014" on a magnum caliber with the recessed cylinder. Measurements should be made after a thorough cleaning.....with special attention being given to the yoke and cylinder assembly.
 
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I've always wondered how you could tell if the firing pin on these types of revolver were too short. I can't imagine how they'd get worn down. If it's hitting center, and it's not the mainspring, I'd try to look at that possibility.
 
Federal primers dent a lot easier than CCI or anything else. If the mainspring looks bent compared to another one, bend it back straighter to look like the other one. A properly tempered spring will stay where you bend it to. If it's bent too far forward, it won't put enough tension on the hammer even with the strain screw tight.
 
Toolguy I agree with your comment about Federal primer hardness. The spring looked bent so I put in a NOS OEM replacement and I hope I it got it fixed.

Only the range will tell.

Thanks for the input guys!
 
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