A few months ago I purchased a 640 Pro and immediately loved it.
I didn't carry it until I got a suitable holster, but I shot it regularly at the range: It shot very accurately, the sights are very quick to acquire the target, and recoil was easily managed even on the rare occasions that I shot full house loads through it.
Last week I put it into an IWB holster, put it on, and looked down to see the rear sight lying on the floor. It all too easily slid back into its retention slot on the frame; clearly it won't stay there for long. S&W customer service is sending me a mailing label so they can fix it; and while I appreciate that I don't think I can trust it even after the repair. The absence of a set screw leads me to doubt that the friction fit base can hold it for long, and it is an expensive sight to replace.
Not one of my other seven S&W revolvers have a weakness in their design like this. Has anyone else had this problem, and if so how did this happen, how was it fixed, and how long did the fix hold?
Thanks for any guidance here!

Never really saw a need for adjustable sights on a 2" J frame.
My M 640 is just the plane Jane and at close range who needs adjustable sights?
Not me....

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Only difference Fool/Mule-ears

It doesn't surprise me since shooting full house loads has a bit of recoil for sure. It doesn't surprise me then for the sight to come loose.
BTW I can't stop looking at my 640-1. It is eye candy for sure. I really like the gun. Yeah no adjustable sights here either. Don't seem to need them.

Obviously something is out of spec. Set up correctly the rear sight should never come lose. I had the same issue years ago with a Colt automatic. It hasn't deterred me from dovetail fitted rear sights. I'm sure S&W will correct it with a correctly sized rear sight or a gun with a properly milled dovetail.

Opposite issue here.
The rear sight on my 640 Pro is ever-so-slightly off center, l tried to center it but it was in the dovetail so firmly I couldn't move it using a brass punch and a mallet. It shoots close enough to point of aim so I decided to live with it for now.


Sent from my SCH-I545 using Tapatalk

Wow, it's not often I get to use one of my favorite idioms in this forum, but the rear sight on my 640 Pro is tighter than Dick's hatband. I can't imagine what would cause it to fall out. Either the sight is out of spec or the dovetail is cut wrong. If it's the dovetail the only way I could see to fix it properly is to replace the frame which would mean a new gun.

Let us know what they do for you.

I wouldn't send it back in. I would get some very thin shim stock and put different thickness under the sight until it's tight. I saw a guy on Midways "how to" videos use this method on a loose front sight. Just a idea.

Like some of the others that have posted, I just have a plain jane 640-1 that has become my daily carry, as least for now. I'm sure that S&W will make it right.

Would it be possible to drill a small hole and install a set screw?

I almost bought that gun because of the sights. And one day I may just do that.
Have Smith fix it up for you. I like the model, just bought too many others.

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Some assembly required..

Two easy repairs: first is to turn the rear sight upside down and use a small metal push to put a couple of dimples in the bottom. The second would be to drill a small hole in front of the sight channel, tap it and put a small hex-head set screw in it with a little blue Lok-Tite.

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Dave Frost

Thank you all for your thoughts and experiences.
I'll let you know how this turns out...

Just to let everyone know, I have received the 640 Pro back from S&W in a reasonable time. They replaced the rear site, and the cylinder as well. Due to the fact that the repairman did not supply any additional advice to the person who communicates by email, I was not able to determine what went wrong with either the site or what they found to be wrong with the cylinder.

The site seems tight now; but it did so before it suddenly loosened and fell out. It will be a while before I can take it to the range, so I wanted to post this update. If I have additional problems after that I'll be back on the forum.

Thank you to everyone who replied to my query.

A friend bought a Kimber Gold match II, rear sight blade fell off after 25 rounds of hardball. He paid to return it to Kimber, got it back, 25 rounds of hardball and the entire sight was gone. This time Kimber paid shipping both ways. He got it back and I have no idea how many thousands of rounds are through it now, but never had a problem, no reason was given as to "why" it fell off. Glad you got the 640 back quickly. Be Safe,

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I BACK OUR BLUE

Dogman, your 640 Pro isn't the only one with a poorly installed rear sight...

My 640 "Professional Series" was shipped new-in-the-box from S&W to me via my local gun shop and I was there when the FedEx guy dropped it off. While completing the transfer paperwork my dealer was holding the revolver to read the serial number when "CLUNK", the rear sight falls off!!!

For those who think the 640 Pro has adjustable sights, they are not. They are a three-dot tritium fixed sight setup as seen below. Apparently some of them have the added feature of being self-removable.

I wrapped it back up and returned it to S&W to fix the rear sight issue along with: a canted barrel; goofed-up caliber etchings on the barrel; and front sight missing most of the white outline.

OBTW, in the several years I've owned my gun it has made four trips back to the mothership and has had two different barrels installed to fix canting issues and low impacts to point of aim.

It is finally shooting where the sights point and all of the new-in-the-box issues are fixed... Is mine a "Friday" gun or a standard gun? Regardless, "Professional Series" has a new meaning for me when it comes to quality control.

Edmo

On edit: Below the pictures I attached a YouTube link of me shooting full power 357 Magnum rounds through my 640 Pro. Spirited to say the least. This was filmed about halfway through the multiple trips back to fix my point of impact / point of aim issue...







Shooting My S&W 640 Pro - YouTube

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TRUTH: Don't delete my posts!