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  #1  
Old 12-29-2023, 12:26 PM
Matt_X Matt_X is offline
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Default Normal Hammer block contact? Model 36

Is it normal to observe some contact marks from the hammer on the back of hammer block?



This is a c.1975 Model 36
I opened it up after having failures to fire (light primer strikes) in double action.

Internals were dirty (see photo), but also looked like the hammer had just kissed the top edge of the hammer block.
Arrows on photo indicated location of marks on block and approximate matching location on hammer.
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Old 12-29-2023, 12:44 PM
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Negative, no it's not normal...
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Old 12-29-2023, 02:38 PM
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If this persists after the thorough cleaning of the internals, you can crown the top edges of the "flag" at the top of the hammer block, and remove a small amount of material from the top of the flag. (note: The illustration is a K series hammer and hammer block, but the modification is the same)

The edge of the cutaway on the hammer, just beneath the hammer nose is not clearing the top of the hammer block as the hammer goes fully into battery.

If the hammer block cavity (hole) at the bottom that fits over the pin in the rebound slide is badly worn, you can always just replace the hammer block with a new OEM one.

Be sure not to cycle the action under pressure from the hammer spring while the sideplate is off. This can result in damage or breakage to the hammer stud, rebound stud or trigger stud.


[url=https://flic.kr/p/2og5ceq]





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Old 12-29-2023, 03:26 PM
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Thank you. Yesterday there was at least one misfire every cylinder when fired double action. So range firing should be a pretty good check. Previous two sessions there were no misfires.


Everything but the extractor and ratchet was removed and cleaned with Kerosene, then mineral spirits. A very little bit of arkansaw stone on rough edges and burrs. Cleaned again and drop of Remoil on bearing and rubbing surfaces.
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Old 12-29-2023, 04:06 PM
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Not to get too far off the trail here, but just a reminder in terms of the many possible causes of misfires in DA..... "staging" the trigger in double action can cause what's called "hammer hits rebound". This "incomplete" rearward travel of the trigger in DA (staging) can result in the rebound seat on the hammer striking the hammer seat on the top of the rebound slide, causing the hammer to not go fully into battery, and cause misfires.

Just another thing to check for.....a little bit of "wink" (space) between those surfaces when the trigger is fully rearward and the hammer comes fully down.






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Old 12-29-2023, 08:58 PM
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Just for S&G's, make sure the hammer is not rubbing up against the frame or side-plate.
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Old 12-29-2023, 10:36 PM
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Funny you mention that. There was evidence of rubbing on the side plate. I lightly went over the plate with a translucent stone and also broke the sharpness of the edge. The hammer I did not touch.


Observations as to whether that amount of contact could be a significant contributor are welcome.


Normal Hammer block contact?  Model 36-36-1_2023-12-28_0513crop-jpg


Normal Hammer block contact?  Model 36-36-1_2023-12-28_0510cropped-jpg
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File Type: jpg 36-1_2023-12-28_0503-hammer.jpg (112.7 KB, 8 views)
File Type: jpg 36-1_2023-12-28_0513crop.jpg (135.7 KB, 262 views)

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Old 12-30-2023, 10:39 AM
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Quote:
Originally Posted by Matt_X View Post
Funny you mention that. There was evidence of rubbing on the side plate. I lightly went over the plate with a translucent stone and also broke the sharpness of the edge. The hammer I did not touch.


Observations as to whether that amount of contact could be a significant contributor are welcome.


Normal Hammer block contact?  Model 36-36-1_2023-12-28_0513crop-jpg


Normal Hammer block contact?  Model 36-36-1_2023-12-28_0510cropped-jpg
Once in a while a shim needs to be added. That rubbing looks to me like it is more than just the hammer block safety! I'd also check to make sure that the hammer is sitting all the way down on the stud. Dirt or debris could be raising it slightly and causing it to sit just a wee bit proud, causing rubbing.

Last edited by chief38; 12-30-2023 at 10:45 AM.
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Old 12-30-2023, 11:32 AM
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If you really want to know if it is the hammer block(which I doubt) simply remove it and fire a few cylinders full.

I am with chief38 in believing your hammer is dragging. Those marks on the side plate and hammer show that.

Armorer951 gave some good thoughts and I will add that you should check for endshake.
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Old 12-30-2023, 01:28 PM
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The only change I can think of between the first two times at the range and the third is additional accumulation and movement of dirt and grit.

That doesn't mean that underlying factors (such as hammer block contact, hammer rub, or rebound contact) aren't at the root of the issue.

I can certainly try adding shim to the sideplate side if there is enough side play.

There's about .004" endshake based on the cylinder gap measurement pushing forward and back; .008 to .004"
headspace is .067"


Shim sources for J-frame shims? triggershims dot com or mcmaster-carr?

Last edited by Matt_X; 12-30-2023 at 01:50 PM.
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Old 12-30-2023, 03:13 PM
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Triggershims.com.

Steelslaver has pointed out a great way of determining if the hammer block is the culprit or not.....just remove it for a test fire session.
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Old 12-30-2023, 05:50 PM
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Quote:
Originally Posted by armorer951 View Post
Triggershims.com.

Steelslaver has pointed out a great way of determining if the hammer block is the culprit or not.....just remove it for a test fire session.
Normally I would agree, but in this case the hammer and side-plate are so marked up (been going on for some time), you would need to coat them with Dykem machinists dye first. If no Dykem is on hand, then a good old magic marker would work. Then yes, that is a good suggestion. Removed with alcohol afterwards of course. Dykem comes off easily as it is made to.
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Old 12-30-2023, 08:05 PM
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That's a great idea. I have dykem and magic markers.

I can feel play in the hammer, so a shim may be a good idea anyway.
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Old 12-31-2023, 11:01 AM
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Matt X,

Don't know exactly what the grease or grit is on your original photo, but it should not be reapplied after solving the issue here. Only a [U]light[/U] lubrication on the pivot and sliding points - that's it! Excess oil and or grease does little to help and lots to hurt because it attracts unburned powder. lint, debris, etc.

I can also tell you that the rearward most mark on the back of the hammer can not be from the hammer block safety because it can not touch it - too far rearward. Must be from side-plate.
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Old 01-07-2024, 02:37 PM
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Who knows what lubes were on the mechanism when I bought it.

Triggershims was a good source. I like that they mark the thickness on the shim.

A few trials for rubbing and binding resulted in two .002 shims on the right side of the hammer. Also a .002 cylinder bearing shim.

While it was apart, here is a little better photo of peening I saw on the hammer block.
I think its good. It will be at least another week before I can get to the range.
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File Type: jpg 36-1_2024-01-07_HB-untouched-0609.jpg (38.9 KB, 45 views)
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Old 02-03-2024, 01:45 PM
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I got to the range and not solved.

As I failed to think out the 'what if' I didn't examine carefully the primers and document at the time. Likewise forgot to bring a screwdriver so I could trial without the hammer block.

However as far as the spent brass goes, there was one that clearly had a light strike. (photo shows a mix of single action and double action fired brass)

There is a little roughness in the hammer block channel, but I would think that a) movement is dictated by the pin on the rebound slide, and b) round slide in double action is in the same position single action.

Next post will be looking at the 'wink' between the rebound slide and the hammer's rebound.
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File Type: jpg 36-1_2024-02-03_1048-cases.jpg (186.8 KB, 22 views)
File Type: jpg 36-1_2024-02-03_1056-block_channel.jpg (257.0 KB, 17 views)

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Old 02-03-2024, 02:00 PM
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There does seem to be a little space between the hammer and the rebound, although less so when releasing double action.

I'll let the photos do the talking here.

First one is with the trigger held at the point where the hammer releases.
Normal Hammer block contact?  Model 36-36-1_2024-02-03_1059_da_release-jpg


Second is with the trigger all the way back.
Normal Hammer block contact?  Model 36-36-1_2024-02-03_1060_trig_back-jpg


Third is contact on with the trigger returning and the rebound slide moving forward.
Normal Hammer block contact?  Model 36-36-1_2024-02-03_1062_trig_return-jpg




This problem only showed up after its third trip to the range.
Only after the failures to fire did I open the sideplate. So whatever changed is probably subtle
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File Type: jpg 36-1_2024-02-03_1059_DA_release.jpg (160.6 KB, 139 views)
File Type: jpg 36-1_2024-02-03_1060_Trig_back.jpg (166.5 KB, 133 views)
File Type: jpg 36-1_2024-02-03_1062_trig_return.jpg (159.4 KB, 137 views)

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Old 02-03-2024, 09:21 PM
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When there is abnormal contact between the rebound slide and the rebound seat on the hammer when the hammer drops in double action, you can usually "hear" the difference in the sound of the hammer impact when it goes into battery.

When the parts are fit correctly, the hammer makes a very clear and loud "click" when it completes it's forward rotation and strikes the frame cutout. When the hammer seat on the rebound slide is a bit too far forward, the sound of the hammer impact is not sharp and distinct.....more like a dull thud.

In this scenario, misfires or "light" primer strikes can often be due to an incomplete follow through on the trigger by the shooter either because of improper trigger technique, or perhaps because of an attempt at "staging" the trigger rearward, instead of pulling it though completely.

If you determine the front of the hammer seat on the rebound is literally "in the way" at the completion of a clean and complete DA trigger pull, you can remove material from the front face of the seat to accommodate the hammer and make a bit more room here. The shape of the seat should remain the same. Another alternative would be to substitute a different rebound slide with a slightly shorter dimension at the front of the hammer seat interface.

Under no circumstances should material be removed from the top of the hammer seat on the rebound slide, as this is a critical part of the primary safety in the revolver.


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Old 02-04-2024, 12:55 PM
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@armorer951 Thank you. All the dry firing had been with dummy cartridges or spent brass. Trying the action both SA and DA the hammer is hitting the frame first. I can't say that was the situation before, but it clears up where that stands now. Now being after I touched up the angle on the front hammer seat so it is even all the way across.

Also, after better shaping the bevels at the hammer block top (again to be even and square all the way across) I coated the them with red Dykem. The red is all still there, so I think that's OK now.

Firing pin protrusion is around .044 or .045" (comparing with feeler gages). Khunhausen writes that he has measured .039 to .045" so I think thats OK. (He also suggests .055 to .062 max should be good, but I infer that is if one is replacing the nose)

Head space is about .063"

Finally, put Dykem on the back of the spent brass with the lightests primer indents ran them through in double action. All look to have decent strike marks now.

I think the next step is to go back the range.

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Old 02-11-2024, 07:51 PM
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This afternoon was the least successful range session since I bought this revolver. There were 2 out of five light strikes in single action, and consistant light strikes in double action.

Normal Hammer block contact?  Model 36-36-1_2024-02-11_light_strikes-jpg

I find this interesting in one respect, whatever is failing is getting worse. Not many mechanical things get worse that quickly.

To recap range sessions and work on gun:
1. 25 shots SA, 35 shots DA. Worked perfect.
Changed from Target stocks to Magna Stocks with grip filler
2. 30 SA, 30 DA. Worked fine
No changes. Just regular cleaning of chambers and bore.
3. 20 SA, 30 DA. Some failures to fire double action
Remove sideplate, clean, and try to identify causes.
Started this thread 29 Dec 2023

4. 10 SA, 10 DA. About 6 out of 10 Failure to fire double action. Second strike in single action generally fired.
Further work discussed above.
5. 5 SA with two out 5 light strikes, 5 Double Action all light strikes. (see photo)
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Old 02-11-2024, 08:30 PM
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You might check:

to see that the yoke is free of any end shake when it's in the gun and the yoke screw is installed.

Take a look at the hammer nose bushing and the condition of the frame cavity where the hammer enters the frame when going into battery. (use a magnifier) Also ck the hammer nose and rivet condition and movement.

Make sure the hammer is moving freely, and entering the frame cutout centered up with the hole in the hammer nose bushing. Could the added shim on the hammer stud be causing issues?

I would also shoot it without the hammer block, to make sure that particular part is eliminated from consideration in terms of the cause of the intermittent light strikes. I believe you already confirmed the protrusion of the hammer nose is adequate, and the rear gauge appears to be in spec.

Just some additional things to look at.



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Old 02-11-2024, 09:57 PM
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Is this with factory ammo?
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Old 02-11-2024, 11:32 PM
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Quote:
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Is this with factory ammo?
Yes. First was a box of Ammo Inc 158 grn MJ, after that mostly Fiocchi 158 gn FMJ. Also ran some Browning 130 gr., Rem 158 gr LRN, Hornady 110 gr FTX to compare POI.
Point of Aim was target center.

The 110 FTX grouped low.
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Old 02-11-2024, 11:58 PM
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Carter,
Thanks. My answers and questions interspersed.

to see that the yoke is free of any end shake when it's in the gun and the yoke screw is installed.

Yoke has no play at all.

Take a look at the hammer nose bushing and the condition of the frame cavity where the hammer enters the frame when going into battery. (use a magnifier) Also ck the hammer nose and rivet condition and movement.

The hammer nose looks OK to me, but I have not any experience here. I only have a 1942 Victory to compare with and Kuhnhausen.

Normal Hammer block contact?  Model 36-36-1_2024-02-11_1233-hammer-jpg

Make sure the hammer is moving freely, and entering the frame cutout centered up with the hole in the hammer nose bushing.

I gently lowered the hammer observing from the back and from the cylinder side. The nose first contacts above the hole and then seamlessly rotates on contact and the nose slides through fairly centered.

Looking into the frame cavity we can see the hammer contact has favored the left side.
Normal Hammer block contact?  Model 36-36-1_2024-02-11_1242-hammer-cavity-jpg

Could the added shim on the hammer stud be causing issues?

I think the answer is yes. One of the shims has deformed. That probably indicates too much pressure.

Normal Hammer block contact?  Model 36-36-1_2024-02-11_1237-washers-jpgNormal Hammer block contact?  Model 36-36-1_2024-02-11_1240-washers-jpg


I would also shoot it without the hammer block, to make sure that particular part is eliminated from consideration in terms of the cause of the intermittent light strikes. I believe you already confirmed the protrusion of the hammer nose is adequate, and the rear gauge appears to be in spec.


That seems like a good plan. Process of elimination. I'm also going to remove one or both of the .002" shims. The range is a cross town so its also an excercise in patience.


Visually the hammer spring looks great. No kinks or divets or any signs of damaged coils. I assume its factory.
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File Type: jpg 36-1_2024-02-11_1237-washers.jpg (111.8 KB, 50 views)
File Type: jpg 36-1_2024-02-11_1240-washers.jpg (143.8 KB, 53 views)
File Type: jpg 36-1_2024-02-11_1242-hammer-cavity.jpg (93.6 KB, 52 views)

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Old 02-12-2024, 12:40 AM
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I've never been inside a J frame so I'm viewing this as a detective/mechanic....

Looking at the wear patterns on the hammer in post #7 (right side top, left side bottom rear of the stud boss) and the left side impact in post 24 makes me wonder if the hammer stud is bent slightly down and to the rear, causing the hammer to sit at just a bit of an angle. Have you been cycling the action a lot with the springs in and the sideplate off?

It could also be that the stud is straight and the mounting hole in the hammer is worn out of round. Does the hammer fit tightly onto the stud? Or does it wallow around a bit?
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Old 02-12-2024, 11:20 AM
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Quote:
Originally Posted by Shotguncoach View Post
I've never been inside a J frame so I'm viewing this as a detective/mechanic....

Looking at the wear patterns on the hammer in post #7 (right side top, left side bottom rear of the stud boss) and the left side impact in post 24 makes me wonder if the hammer stud is bent slightly down and to the rear, causing the hammer to sit at just a bit of an angle. Have you been cycling the action a lot with the springs in and the sideplate off?
The accumulated dirt inside was sufficient clue for me to conclude the sideplate had not been previously removed. And even if so, not regularly opened and cleaned by the previous owner.

I have never cycled with the side plate off and the hammer spring installed.

Quote:
It could also be that the stud is straight and the mounting hole in the hammer is worn out of round. Does the hammer fit tightly onto the stud? Or does it wallow around a bit?
There isn't much if any room for play with the hammer stud to its sideplate support. There is some play between the hammer stud and the bore in the hammer itself. Enough that when there is no spring installed there is hammer can be slightly wiggled side to side. I doubt the hammer wears because it is hardened. Stud wear is possible but I *think* the stud in question has not seen a lot use. I *think* the play is typical but someone with experience will have to answer that.

My understanding is the sideplay is limited by the bosses of the stud supports. When installing the hammer shims, the play is taken up until there is no movement and then remove .001 to .002" of the shimming.

The contact on the side of the hammer shown in the earlier photos is certainly in part due to the allowable play in the hammer, and in part due to the rough finished (unfinished) surfaces inside the frame and sideplate.




As far as hammer contact inside the hammer recess of the frame - I can't answer. Hopefully Carter or some others with experience will have some insight there. However note that the wear through the bluing is cumulative from the life of the gun. I didn't think to go over that location with a marker or Dykem.

Last edited by Matt_X; 02-12-2024 at 11:26 AM.
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Old 02-12-2024, 02:48 PM
S&W revolverman S&W revolverman is offline
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Normal Hammer block contact?  Model 36 Normal Hammer block contact?  Model 36 Normal Hammer block contact?  Model 36 Normal Hammer block contact?  Model 36 Normal Hammer block contact?  Model 36  
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Just to add to all the great info already offered,
the factory J frame mainspring should have 26 coils.
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