Hammer or nose moving?

[ToddG]

I picked up a 66 no-dash that had a trigger job and jeweled internals. Someone took their time with this baby. Very smooth in single and double action, but for one out of every 10 shots or so the hammer nose strikes the very edge of the primer, not enough to ignite. Only happens DA. SA, while wildly light, doesn't seem to have the problem.

Full teardown and cleaning out old gummy oil inside helped some, but still getting those off-center strikes that fail to ignite. Pics show one of the edge strikes and one of the solid strikes that did fire. Other pic are the 5 that lit as normal. Strike looks solid on those. Put the bad strike cartridge back in and it fired just fine in single-action.

The hammer and nose feel looser than some of my other 66s, but about the same as others. There is a shim on the right side of the hammer but not the left.

Suggestions before I start swapping parts from other 66s to see if I can narrow it down?

Also, any suggestions on where to get another shim for the left side, or a set of shims to better stabilize the hammer?

 

[s&wchad]

Looks like a timing issue. If it's hitting right/left of center, a new hand and/or cylinder stop should do the trick.

 

[ToddG]

Huh. Didn't think about timing, but that makes sense. I'll swap from a well-functioning 66 and check.

Thanks!

 

[GerSan69]

I agree. I had a 67 with a timing problem - symptom was the offset firing pin strike as shown in your photo.

 

[WR Moore]

Depending upon the skill level of the individual who did the "action work", there also might be issues with the hand off from the primary double action sear (spring loaded lever on the front of the hammer) and the secondary double action sear.

If you watch the hammer/trigger during a double action firing, the primary DA sear starts the hammer backward. At a point close to releasing the hammer, the engagement changes to the bottom of the hammer "foot" and a trigger surface below the single action sear.

If the work wasn't done properly, the interaction between hammer & trigger might might not be correct and the hammer drops before the cylinder is properly aligned. This can be helped along by your failure to complete the trigger press. Stopping short of the trigger being all the way back usually results in the hammer/trigger catching and causing misfire, but the hammer strike is still well centered.

Just to cover all bases, check the firing pin/hammer nose bushing in the breech face/recoil shield. The hole should be round or real close to round. If it is, the hammer nose has nothing to do with your problem.

Being persnickity, it's carryup not "timing". Checking the hand fit is a good idea. Knowing if the off center hit is 3 or 9 o' clock will let you know if there's a problem with the cylinder stop.

 

[Steve912]

Here's something to check for, on timing.

I picked up a Model 64 "police surplus/return" earlier this year, my
first revolver.

Initially it timed up fine, but after a few weeks of live & dry fire, I saw
hits on fired cases starting to show primer dings spread across the
case heads, like your pic. The spread started fairly tight (across face
of primer) but grew wider (across entire case head width) alarmingly
fast.

Eventually found the cylinder stop was doing a slow-motion rise to
it's lock position, allowing the hand and/or inertia to rotate the
cylinder past where the stop should have caught & locked it.

Turned out the stop was a MIM replacement part (in a 64-3), and
had a big "circled 2" marking on side opposite the side plate. This
raised, sharp marking was dragging up a scarf of steel off the frame,
as it rocked back and forth. The draggy scraped area created enough
friction that the stop's rise was a slo-mo event, instead of a "snap",
after slipping off the trigger nose.

I stoned the "circled 2" off the stop and slightly smoothed the frame
between stop boss and trigger, and the timing returned to normal.

 

[tg4360]

I vote timing.

Check to see where the strike is clockwise on the cartridge before you extract them AND see if it's the same chamber every time.

I suspect it will be.

 

[Hondo44]

Do this simple check:

Cock the hammer slowly and confirm the cylinder locks in position for each of the 6 chambers about the same time the hammer cocks. If satisfactory, now operate the gun in DA pulling the trigger very slowly; again confirm the cyl locks before the hammer drops. After each cycling of the action, confirm that the cyl is still locked in position for all 6 chambers.

 

[ToddG]

Thanks all. Hammer nose bushing is nice and round.

But, when pulling back the hammer slowly it cocks just before the cyl locks. It takes a bit more pulling back to lock the cyl.

On a slow DA trigger pull, if the cylinder stops before the hammer drops I can't see or hear it. It seems to stop just as the hammer drops. Pulled out a tight 66-1 and can definitely hear a locking click before the hammer drops. The cyl always ends up locked, tho.

I can see both the hand and stop have been filed. I guess the 'tuner' took a couple of swipes of the file too many. I'll swap in a different hand next weekend and see if that cures it.

Great test, Jim, and thanks again to all for the guidance.

 

[Hondo44]

Todd,

Great trouble shooting. Now your on to the fix.

 

[243winxb]

Does the early model 66 have a hammer nose spring? If missing, the nose may strike at 12 oclock?

 

[s&wchad]

Does the early model 66 have a hammer nose spring? If missing, the nose may strike at 12 oclock?

No, a six or twelve O'clock strike isn't really possible. The front of the hammer nose bushing is round and only slightly larger than the tip of the hammer nose. The back of the bushing has a lead that guides the nose into position. Premium revolvers had the spring, but many did not.