Fixed a S&W K-38 today

[rcmodel]

And I still have no idea what I did to fix it.

Gun is a like new 8 3/8" 14-2 a friend brought by.
Problem was severe trigger slap when fired SA.

DA was perfect.
But you couldn't keep the trigger back when the hammer broke SA!
(Almost like a mechanical impact from the hammer.)

So:
1. Checked the strain screw but it was tight. (still did it)
2. Oiled and blew it out. (still did it)
3. Pulled side-plate and couldn't get it to do it.
4. Put the side-plate back on without the screws and it still did it about 50% of the time. (No unusual rub marks inside the sideplate or frame.)

5. Pulled the hammer and checked the DA fly. (Nothing to see there)

6. Completely dissembled, and couldn't find anything except a little black grunge inside the rebound slide. (Spring was clean and lightly oily but no metal chips or burs I could find with a Q-Tip.)
7. Re-lubed and reassembled, and worked fine with the side-plate off.
8. I put the side-plate back on and cinched all the screws and it still worked fine.

And still worked fine after about 250 SA dry-fires.


SO whatever it was, it eluded me completely????

Don't think I ever had that happen before where I still don't have a clue what was causing it, or what I did to fix it! :banghead:

Anyone have any ideas??

rc

 

[Bull Nutria]

that revolver succumbed to the RC knowledge and mojo! so self respecting S&W revolver would dare act up and not work perfectly after the master laid hands on it!!

Way to go RC!!!

Bull

 

[Old Fuff]

I suspect the double-action sear was sticking and bumping the trigger on the way down. It's hard to diagnose when it doesn't happen consistently.

Removing the side plate may have allowed the hammer stud just enough movement to give the sear the clearance it needed.

File just a hair off the front face of the sear and see what happens. Also be sure the spring and hole in the hammer is free of gunk and the spring isn't bent or twisted.

 

[rcmodel]

No, the DA sear was not sticking, and not even close to hitting the hammer.
No abnormal marks on it anywhere from sticking in the hammer, or hitting anything it shouldn't.

I'm thinking now it had to be something in the rebound slide hole binding the spring part of the time and doubling the force on the back half of it.

But I didn't find anything except some black greasy stuff inside the rebound slide.
But none on the spring, or any indication of bent, or rubbing inside the slide.



It must have been factory buffing compound or ground up scale left from heat treating, as the rest of the innerds where white glove clean, with just a light film of clean oil.

At any rate, there was nothing else even close to black inside the gun anywhere else.
Like I said this was a almost unfired new gun that just suddenly started doing it last week.

In hindsight, I should have polished out the spring tunnel instead of just cleaning it with a Q-Tip & solvent.
But I didn't.

If it comes back, I will!

rc

 

[short barrel]

My goodness! A K-38. That takes me back to the good old days. I had a 6" and shot competition in the 70's. A gunsmith there told me I needed to "fix" it by removing the thingy that kept it from firing when dropped. I heeded that information and came away with a very slick competition gun. That's a firearm that I surely wish I still had.

 

[rcmodel]

Your 'gunsmith' steered you way wrong on that right there.

The S&W hammer block has absolutely nothing to do with the trigger pull.

It just keeps you from killing yourself or someone else if you drop it on the hammer hard enough to shear off the hammer stud & bypass the redound slide hammer block.

There is no logical reason to EVER remove the hammer block to make a better trigger.
EVER!

It doesn't even interact with the trigger or hammer.
It operates off the rebound slide, and does nothing to change the trigger pull when the hammer is cocked and the trigger pulled.


rc

 

[Jim K]

Hi, rc,

If you still have the gun, check the trigger stop. If it is the kind that is in the frame, those often fix themselves when the gun is being worked on, but the problem may occur again at any time. Either make sure the darned thing is tight, or take it out altogether and replace it with the pin inside the trigger return spring (rebound slide spring).

Jim

 

[rcmodel]

Good advice Jim, and I meant to do that, as that would be one of the first things I tell everyone else to do.

But, apparenty I don't do as I say, when it's me focused in on something else I think must be wrong.

I checked for a trigger stop rod when I took it apart.

And it never even entered my mind to look for the troublesome frame mounted trigger stop I warn everyone else about!

I'm losing it in old age!!!! :banghead:

PS: I do remember there was quite a bit of over-travel after the trigger break, so probably not that unless it was loose and bouncing back and forth.
I'll check next time I see him though.


rc

 

[Jim K]

Believe me, you are not the only one losing it. I asked my wife just this morning, "What is my name, again?"

Jim (I think)

 

[rcmodel]

Update:

He called me yesterday and said it worked perfectly for 50 rounds.

Then he call me again today and said it started doing it 50% of the time again!

He is going to bring it back for another look see.

Gotta be the trigger stop moving around, or something still floating around inside the rebound slide loading the spring up?

Maybe?

rc

 

[Jim K]

That trigger stop arrangement is weird. The screw does not hold it down; instead the threads are in the stop itself and the screw pulls it up against the right side (top when you are working on it) of the slot. Not a real good arrangement. As I have posted elsewhere, I fixed a few by making a new one that filled the whole slot with just a tab sticking out. Then I drilled and threaded it to keep it solidly in place. With the gun back together, I filed the stop down a stroke at a time until the trigger released the hammer. A lot of work, but a real solid fix and I thought better than the pin inside the rebound slide (which, I confess, I didn't think of).

Jim