Normal Hammer block contact? Model 36

[armorer951]

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.



Carter

 

[ms]

Is this with factory ammo?

 

[Matt_X]

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.

 

[Matt_X]

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.

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.

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.




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.

 

[Shotguncoach]

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?

 

[Matt_X]

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.

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.

 

[S&W revolverman]

Just to add to all the great info already offered,
the factory J frame mainspring should have 26 coils.

 

[Matt_X]

Some improvement at the range.
Out of 70 rounds double action without the hammer block, there were 7 failures to fire on the first strike.

With the hammer block installed, there was one failure to fire out of 30 rounds double action. Five of those were Browning cartridges (winchester brass) and may have softer primers.

So the hammer block is not delaying the hammer now, if it ever was.

The chamber was not the same from one misfire to the next.

With the sideplate off at the range, there appeared to still be some contact of the hammer with the frame and sideplate. Will get a better look tonight.

 

[Matt_X]

And a little deeper look confirms marker has been rubbed off.
Although the bluing inside the frame where the hammer goes is there.

A thought came to me while thinking about pressure from the spring possibly pushing the hammer toward the sides. Is something not centered or squared?

How about the hammer spring's strut?

 

[armorer951]

Please excuse my poor memory, but have you already confirmed that the hammer spring is an OEM mainspring? (closed and flat ground at each end)

Can you check to confirm there is no impact (touching) of any part of the bottom of the hammer to the top of the rebound slide when the the hammer goes fully into battery? That impact could be intermittent. The stirrup of the trigger can put quite a bit of upward tension on the rebound, if the stirrup is not straight. In this case the stirrup can push on the front of the rebound at an odd angle....sometimes even a slight upward angle, which could cause the rebound to be in the way as the hammer comes down.

Can you measure the overall height of the rebound slide, from the bottom, to the top of the hammer seat?

Also, I'm wondering if you mark the sides of the hammer and dry fire with the sideplate on, where the scuffs are. If the hammer is scuffed, what if you mark it and then dryfire without cinching down the sideplate.... leave the back two screws backed out a full turn. Does the hammer still get scuffed in this scenario?

Thanks

Carter

 

[Matt_X]

Carter,
I appreciate the questions. It can be hard to keep track of other people's projects especially when days or weeks go by between posts.

Hammer Spring: Seems to be ground flat, 26 coils, but I'll remove it from the strut this morning to check it.

Hammer Spring Strut: See the photo in my previous post? It sure looks bent. Perhaps a clue someone was in there before me and leaned or pried on it??

Could that be pushing the hammer to one side?

Hammer to Rebound Slide Contact
The photos from before are about as well as I can see.

It looks to me like the trigger stirrup is pushing the rebound slightly downward. When I remove the rebound slide we can take a look for side bending.

Hammer side scuffing
Interesting experiment you suggest. Will try that this morning too.
When I removed the sideplate to instal the hammer block the yoke and center screws were not tight. So the last 30 shots were fired with tight screws as well as the hammer block.

 

[Matt_X]

Main Spring Dimensions:
I count 27 1/2 full coils. Photo below so others can check my counting. For calculating spring rate, active coils are based on total coils less end coils. But if someone has a factory spring they can check for total coils and if the end finish matches, that would be really helpful.

Free Length = 1.730", Coil Outer Dia. = 0.205", Wir eDia. = 0.033"
Measurements are with a cheap dial caliper so plus minus .001"

Hammer Spring Strut:
a. Bent in middle.
b. Yoke is rounded over with a bevel on the side which is bent inward. Could it be so soft that it is wear? Or someone's filing?

 

[Protocall_Design]

The bent strut is not helping anything. It needs to be flattened out. It is part of the problem, but no telling what percentage. Possibly a low percent.

 

[Matt_X]

Fair enough. Thank you.

It was softer than I expected. Its flat now and the corners light stoned.


On Jack's First there are both flat struts (Stirrups) and round ones. Presumably the flat versions are were made later for cost savings?

He also has a photo of factory springs. Some are in the white and others in the black. The top shiny one is 26 coils by my count, and the blued one at the bottom is 27 + coils. Its free length seems to be a fraction longer than the one I removed.
Smith & Wesson old model J frame 1957-1988 >> Jack First Inc. - Page 3

 

[Matt_X]

The stirrup of the trigger can put quite a bit of upward tension on the rebound, if the stirrup is not straight. In this case the stirrup can push on the front of the rebound at an odd angle

There's a little bit of side play but nothing that looks bent.

Can you measure the overall height of the rebound slide, from the bottom, to the top of the hammer seat?

0.281"


Hammer stud diameter = 0.122"

 

[armorer951]

The overall height of the rebound looks a bit high, but not out of spec. The ones I have here are .278".

Is the peening still happening to the hammer block flag? The photo in post 15 looks as if the corner of the hammer cutout just below the hammer nose is striking the flag as the hammer drops. That shiny artifact shouldn't be there.
Perhaps you could try substituting a different hammer block?


Carter

 

[Matt_X]

Minor but maybe helpful changes upon reassembly.
Main Spring was assembled to strut with the paperclip on the opposite side of the chamfer. My reasoning is this chamfer allows clearence for the rod's yoke to be assembled into back of the hammer without bending.

A little more honing to remove edge burrs on the sideplate.

All of the scuff areas were cleaned and coated with red dykem. (red because the blue went bad).

Revolver was assembled. Sideplate screws were backed out 1 turn each. Stocks were installed without retaining screw. About 30 double action dry fires (with spent cartridges installed).

No scuffing of the Dykem observed except maybe a little on the right and top of the firing pin nose.

 

[Matt_X]

Reassembled with the sideplate screws tight.
Again no scuffing observed after 25 trigger pulls except at firing pin nose and a little on the hammer block chamfer.

Since the higher percentage of failures to fire occured without the hammer block installed, if that's a contributor to the problem its a more minor one.

It seems to me straigtening and inserting the main spring strut the other way has helped.

I think its still possible the rebound needs a little more chamfer. Maybe before touching that it might be worth experimenting with a .003 hammer shim instead of the .002" although .004 was certainly too thick.

 

[armorer951]

The continued inconsistency here, both in SA and DA sounds to me like the rear edge of the rebound seat on the hammer is hitting the front edge of the hammer seat on the rebound as the trigger is pulled fully back, and hammer attempts to go fully into battery. The images are excellent, but this my gut feeling, if there is such a thing.

Of course, as always, this is very hard to diagnose without hands on.

I can send you some new components if you would like to try switching some parts out one at a time.

 

[Matt_X]

The continued inconsistency here, both in SA and DA sounds to me like the rear edge of the rebound seat on the hammer is hitting the front edge of the hammer seat on the rebound as the trigger is pulled fully back, and hammer attempts to go fully into battery. The images are excellent, but this my gut feeling, if there is such a thing.

I can see what you are saying when I observe the relationship pulling trigger very slowly to thet point of releasing the hammer.

If it makes a difference, the only time single action failed was with two 0.002" hammer shims (.004" total) on the right side. This last session I shot one full cylinder single action, plus cleared a failure to fire using single action. So I think single action back to working.

Of course, as always, this is very hard to diagnose without hands on.

I can send you some new components if you would like to try switching some parts out one at a time.

That sounds like a good idea and I appreciat the offer.

Would it make sense for me try a little more work on the rebound's chamfer first?