sight for a 640


Evyl Robot
July 1, 2008, 11:44 AM
Hello, all!

Two weeks ago, I purchased a 640 for my wife to carry. I seriously love that little revolver, and see one like it in my personal future! The biggest complaint that either of us has on it is the front sight. It's got a black ramp on it, and it's just difficult to sight in quickly. Have any of you had a problem like this, and what would you suggest for an alternative? Thanks!


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July 1, 2008, 12:18 PM
Since the 640 has a pinned front sight, it is easily replaceable.

Besides my 640, I also own an M&P 340--and I really like the small-sized tritium front sight on that one.

Call S&W support.

They will know what sights will fit the 640, but they may get their undies in a bundle looking for the correct height--e.g., to get it to shoot to the correct POA.

Unless you have your typical SD ammo sorted out, just tell them it's for a standard 158-gr. load; I've found many SD rounds have been tweaked to match that POA.

Jim H.

Evyl Robot
July 1, 2008, 12:40 PM
A tritium ramp would be sweet on this one! I believe that I will call S&W and see what they suggest. Thanks, Jim!


July 1, 2008, 01:47 PM
Have you considered XS Express Big Dot or Standard Dot tritiums?

July 1, 2008, 08:17 PM
Ditto on the XS sights, can't go wrong with either standard dot or big dot although the standard dot seems to be more proportional with rear sight slot on the M640.

A. E. Hertzler
July 1, 2008, 09:48 PM
I agree with the XS big dot.

The gunsmith at Gander Mountain put the sight on for me. I put the ghost ring on my Marlin 1894 myself, but the guys at XS told me that the pin is not consistently placed on the 640, so they ship it undrilled and they recommended that I have a professional install it.

I would also encourage you to get the Crimson Trace laser grips for it. I like the LG-305 and have it on all my snubbies (640, 642 and 60).
It is a little bigger and allows a better grip. But others like the smaller one.

Either way the laser and Big Dot make a good combination that will serve well in all light conditions.

Evyl Robot
July 13, 2008, 08:29 PM
She says she wants a gold bead. I think that would work well.


Owen Meany
July 14, 2008, 09:35 AM
Evyl Robot said:

She says she wants a gold bead.

Talk her out of it. I know that sounds a bit arrogant, but there are far better options available. I cannot see any reason to give up the option of having tritium for low light use. Gold bead sights may look chic (and work well in some lighting conditions), but a white dot/tritium vial combination sight is highly visible in all lighting conditions, from bright light to low/no light.

Please do yourself and her a favor and put an XS Standard Dot sight on the 640. I have Standard Dots on two 640s and a 340PD and wouldn't part with them for love or money. For me, the dot is the perfect size relative to the J-frames notched rear. Visibility is fantastic, and accurate shooting is no problem (provided the shooter is capable of it) out to 25 yards or more.

And yes, before purchasing the Standard Dots I agonized quite a bit over the Standard/Big Dot issue, and am very pleased that I didn't allow myself to be won over by the high-pressure salesmanship on the XS website, where there is (or was at the time) a FAQ page that all but forced the Big Dot down people's throats. If I recall correctly, it even resorted to ridicule of those who opted for the Standard Dot by opining that most such purchasers were "game-players" who "only shot at stationary targets" or some such demeaning nonsense.

In fact let me bestir myself and see if I find that page.

Yup, here it is, from the XS website FAQ. The below quote can be found at its original location here:

FAQ #1

Big Dot or Standard Dot?

With so many selections how do you pick the one that is best for you? First off let’s go over the basics.


These situations for the most part occur at 21 feet or less, usually a lot less. Department of Justice annual reports state that 90% of police shootings happen at this range or less. A study of shootings over 100 years in New York City have more than 90% of shootings at 10 feet or less. The DOJ study includes figures from sheriffs departments and highway troopers and Border Patrol. Encounters by these agencies can occur at longer ranges (more than 21 feet but less than 25 yards) so they will skew the average range figure a bit.


In the “when” category, about the only common denominator was that light conditions were less than adequate. In our own research we found there was a gap in the visibility of most sights on handguns. Plain black sights rely on having sufficient ambient light to see them against a contrasting background. Such target sights are black and meant to be aligned against the white of the target paper and held in reference below the round bull of the target. This is fine until the background becomes the blue, red, plaid, etc of clothing and then the sight blends in to the point where it might as well be invisible. Contrasting inserts help but are generally too small to be readily seen. Night sights were a big help in low light to no light situations. But since the tritium vials are a weak source of light it does not take much ambient light overpower them leaving you unable to adequately see them in the half light to low light realm. And because they are installed in the same place where a contrasting color insert might be, they remove the ambient light reflector that you might have used in this half to low light range.

What happens that is so different?

If people were only attacked by static pieces of cardboard, then we wouldn’t build our sights the way we have. The same can be said if all shooting situations gave you a walk through before hand and if everybody involved was clearly marked as to whether they were SHOOT or NO-SHOOT people. But they don’t so you’ll have to have to make a whole bunch of decisions, in the moment and on the fly. What you’ll need is information. Information like body language, intent in the eyes, movement of the hands, and/or are there threats from other directions? This means that your eyes will be bouncing all over everywhere except on your sights. Only if a point is reached where deadly force is required, will you need sights and the time it takes for your eye to shift back to find them and get them on target is critical. The stress reactions by your own body are working against you quickly finding your sights. Proof that you can easily miss a man-sized object at 3 feet is found by looking at police qualifying scores versus percentage of rounds that hit in actual gunfights. Most LE Agencies require that officers qualifying score is at least 70% of the possible total, while the average number of rounds that actually impact is less than 15% of those fired. If this isn’t a clear indication that what works well on a target range under target conditions is next to useless under tactical conditions I don’t know what is.

What we offer:

Shallow “V” express rear notch.

This eliminates the billboard found on each side of a standard notch rear sight. You have better access to the front sight and it is impossible to hide the front sight behind the rear sight. The “V” is not a bull’s-eye sight and you will not get the same tiny groups that you can get with such sights. You will get plenty of tactical accuracy and not take forever to find and align the sights in doing so. The vertical bar in our sight is readily distinguished from the front dot. This eliminates any confusion as to which dot is the front sight. Available in the 24/7Express series our most popular sights can be had with this bar as a tritium element.

Big white dot with tritium (Big Dot Tritium/BDT).

The bigger sight is easier for your eye to pick up. Easier to see when your focus is out beyond the front sight locked on the possible threat. The large white area is huge reflector of ambient light and will be seen way on down into the very low light range. At that point the tritium vial in the center of the dot comes into play and begins to take over the sight reference duties giving you a positive front sight reference on down into the no light spectrum.

A better Point of Aim (POA) / Point of Impact (POI) system.

When your eye is making that shift in focus it will lock onto the brightest thing first. The brightest part of the dot is the center. Placing that over the desired point of impact is a natural reaction. From 15 yards on in our POA/POI is center of the dot. As the range increases and you have more time for a refined sight picture we take advantage of your pistols ballistics. Bullets start out below line of sight and the barrel angle is such that they rise to line of sight. By having the under 15 yards POA/POI at the center of our dot then as the range increases to 25 yards the bullets flight will take it to near the top edge of the front sight. Now you have the best of both worlds. A stress sight picture that is quick and easy to find and index on the target and a more precise POA/POI when you need it at longer ranges.

The Standard Dot Tritium.

We have it around because no matter how logical and sound the Big Dot system is you just can’t convince everyone as to its advantages or that you really can shoot accurately with it. The Standard Dot Tritium gives them a better front sight so they will have some improvement. We sell quite a few of them to the gamers who want a better front sight but shoot in a world where the targets are generally static and clearly marked as to which ones are hostile and which ones are not.[emphasis added]

Well, I suppose if they've convinced you to go with the Big Dot, so be it. It's a lot better than a gold bead sight, which I hope you decide against.

Evyl Robot
July 20, 2008, 10:09 PM

The reason she wanted a gold bead is because she loves the one on her 627PC. That being said, I have tried to convince her on tririum. The other night, I took her out on the porch in the dark for a comparison. Her gold bead was completely invisible, and the night sight on my 586 was bright and very visible.

She said that her only complaint about it is that it is difficult to sight in full light, being a black ramp. Last time we were at the gun shop, I showed her the tritium sights with the white ring. I think she's sold. Thanks for the input, and it looks like we're going to get her the tritium.


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