639 rear adjustable sight disassembly

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Wisold

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Hi all, I have a 639 that was stolen 3 years ago. The police recovered it and I got possession of it a few days ago.
I expected for it to be impossible to recognize, all rusty and beaten up, but... It was very dirty but in good condition.

Seems like it was never cleaned, and there were worn marks that I see as happening after thousands of rounds.
The barrel came out shiny after cleaning. The clip foot was bent probably went the gun was dropped. The slide is scratched (not deep), the mouth of the barrel have a nick that does not touch the lands.

The rear sight plates with the U notch and the lateral wings are quite dented. I would like to remove the parts to work on them, maybe replacing the U notched plates, but...
I could not find in the internet an explanation on how to do it.

I don't dare to use my imagination for this task. I once tried to work on the innards of the 639 and I ended sending it to S&W for reassembly.

Do any of you know where I can find the instructions to remove the 639 adjustable rear sight?
Much appreciated.
 
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I have this if it will help. It shows most of the parts that go "SPROING".

The adjustable part comes partially loose with the two spring loaded plungers (36,37,40). Do this in a plastic bag.

Then you should be able to undo the setscrew (28) that holds the base in place. Then it may come out left to right easily, or not so easily. There are additional springs UNDER the base that need to be retained, two different sizes. Another job for the plastic bag. Get them back in the right place !
 

Attachments

Thank you Bruce for the drawings.
I think that if I push in part 36 it will come out of the hole in the protecting wing (same for both sides) and then I can remove the adjustable part. I don't need to remove the rest from the gun. It seems to me that there are only 2 springs in this case.
Bruce, if I do that there will be other things to take care of? Things that will fly out of range?
Appreciate your help.
 
You will need to retain those pushers and their springs, and as you lift the adjustable part out of the sight base, 48,49, 50 (page 2) which are the detent for the elevation screw will want to disappear as well. Like I said, put the whole slide in a big baggie and work inside that, it keeps most parts in the same zip code.

If you don't remove the sight base from the slide, you won't need to worry about those springs.
 
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I saw the drawings and now I understand about those parts. Yes, a bag will be used!
I will not be able to touch the sight for two weeks, but when I do I'll report the results.
Thanks Bruce.
 
S&W 639 Rear Sight Base Removal

How the devil do you remove the rear sight base from the slide on a S&W 639? I have taken the adjustable sight off and removed the screw that appears to hold the sight base onto the slide but the sight base doesn't budge and I don't want to force it. Does it need to be knocked L-R out of the slide groove? Thanks for any help.
 
Yes, still need to know how to remove the sight base from a 639. Thanks
 
Have just left it alone until I found out right way to take it off. Have a new sight base to replace the old one with.
 
Hi, jerryn!

It has been my experience that the adjustable sight bases are not fitted very tight to the slides, however, because of the relatively large interface between the base and the slide, a little bit of corrosion can go a long way to binding these things pretty tight.

When I encounter a stuck adjustable sight base, my procedure is to soak the area thoroughly with penetrating oil for several days.
Then I remove the safety assembly and clamp the slide in a padded and solidly mounted vise (the heavier the vise, the better).
Then using a brass or aluminum drift and enough hammer, I drive the base off from left to right, all the while being careful to alternate my blows between the front and rear of the base so as to drive it out straight and not let it angle or bind in the dovetail.
Once it starts moving, it usually come out pretty easily.

John
 
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I agree with John completely but will emphasize that the slide be mounted solidly in a padded vise and use about a 10 or 12 oz. hammer to get the mount moving. Once it starts to move you can go to a smaller hammer if you wish. I use a triangular shaped brass drift and hold it as low as possible on the base just above the sight cutout in the slide. The most difficult part is to get it moving. Good luck!

Rick
 
For a plastic bag to use in disassembly, I find the ones that come around clothes returned from dry cleaning are comfortably large so you can work in twithout being cramped.
 
Thank ya'll. Had thought it came out of the dovetail the way ya'll said but didn't want to force it. Will give it a go after the holidays.
 
JohnHL said:
Hi, jerryn!
I
When I encounter a stuck adjustable sight base, my procedure is to soak the area thoroughly with penetrating oil for several days.
Then I remove the safety assembly and clamp the slide in a padded and solidly mounted vise (the heavier the vise, the better).
Then using a brass or aluminum drift and enough hammer, I drive the base off from left to right, all the while being careful to alternate my blows between the front and rear of the base so as to drive it out straight and not let it angle or bind in the dovetail.
Once it starts moving, it usually come out pretty easily.

John
Click to expand...

Depends upon how the sight is mounted. Per the patent drawing posted above, the sight base is bolted to the slide. In that case, you're gonna break stuff. You need to verify both that there's a dovetail and make sure the elevation screw doesn't go into the slide. The Bo-Mar low mounts generally do this.
 
WR Moore said:
Depends upon how the sight is mounted. Per the patent drawing posted above, the sight base is bolted to the slide. In that case, you're gonna break stuff. You need to verify both that there's a dovetail and make sure the elevation screw doesn't go into the slide. The Bo-Mar low mounts generally do this.
Click to expand...

Had you taken the time to read this thread, you would have discovered that removal of the hex head set screw retaining the sight base, was covered in post #2.

John
 
JohnHL said:
Had you taken the time to read this thread, you would have discovered that removal of the hex head set screw retaining the sight base, was covered in post #2.

John
Click to expand...

John, had you taken the time to actually look at the patent drawing, you'd have noted that it isn't a set screw, it's a bolt that attaches the sight base to the slide. Also that no dovetail was present on the sight base. There's another thread that shows the sight base with the sight itself removed and the attachment torx head bolt is clearly shown.
 
WR Moore said:
John, had you taken the time to actually look at the patent drawing, you'd have noted that it isn't a set screw, it's a bolt that attaches the sight base to the slide. Also that no dovetail was present on the sight base. There's another thread that shows the sight base with the sight itself removed and the attachment torx head bolt is clearly shown.
Click to expand...

I have Dwayne Charron's patent drawing in my files.

I have repaired quite a few of these S&W adj. sights.

I used BruceB's terminology for the Hex Head Cap Screw that retains the sight base.
Definitely NOT a "torx head bolt" (?!?)

And the sight base is unquestionably mounted in the slide dovetail.

Otherwise, thanks for your thoughtful clarifications.

John
 
As so many people have asked, and I just finished doing this myself on a rusty old 439, I wanted to post a few pictures so it might help someone else.

As mentioned above, you mash in the two plungers on the side and slowly raise the sight. DO THIS IN A PLASTIC BAG or be really careful. That front plunger and spring will FLY! I found this out the hard way, thinking I could stop it with my fingers.

sight1.jpg


This shows the little allen nut you have to remove

sight2.jpg


Here it is flipped over

sight3.jpg
 
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I recently worked on the adjustable rear sight of my "new to me" 1006 & will add some additional info that might be useful.

The rear sight blade & it's windage screw are not the same as on S&W revolver adjustable sights even though at first glance they might appear so. However, the windage screw's nut is the same as the ones used on S&W revolver adjustable sights.

I wanted to replace the 1006's rear blade as it had some minor damage. The new replacement 2-dot blade I purchased did not come with it's dots painted; weird. Because it's rear dots were slightly smaller than the front dot I decided to just go with a white outline rear blade used on the revolvers, which I had an assortment of on-hand.

The auto blade's threads are the same, diameter & pitch, as on the revolvers. The revolver's blade fits but are too wide (.530" vs .495") to allow it the full range of adjustment so each end to the blade needs to be filed down, contoured & blued to shorten it up.

Once reassembled the nut needs to be staked on the screw the same way you do on a revolver by slightly flaring the screw's hollow end where it pass thru the nut, so it won't come off when adjusting the sight's windage.

.

xlarge.jpg


.
 
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