Hello

I need a little info on a S&W 646. I purchased this handgun new a number of years ago and have not fired it. Also after I purchased the weapon I ordered from S&W a extra barrel and cylinder.They really balked at selling me the parts, but did. I tried to find a gunsmith to convert it to 10mm. No takers due to liability. They all said the L frame & titanium cylinder could not handle the 10mm pressure.

How many of this model were made?
Are moon clips still available?
What is this thing worth?

If I could complete the conversion I would probably keep it.
Any info appreciated.

Mike C

Moon clips are still available from a source such as Ranch products. As for converting it to the 10mm, I'd be inclined to side with the gunsmiths, with the higher pressure of the 10mm you may be trying to get too much out of it.

Personally, I wish that they still made the 646, I happen to like the 40 S&W. However I'd prefer a steel cylinder because I've seen what can happen to a titanium cylinder if the protective layer is breeched. One tip if you decide to start shooting it, NEVER use anything more than a nylon brush and a mild solvent on the face of the cylinder . In simple terms let it carbon up, one small scratch through that protective layer will start that titanium burning and titanium has an incredible affinity for oxygen.

It depends on which 646 you have. They made a PC model with slab side barrel that should bring close to a $1000.00 or better and a non PC model that has full lug heavy barrel which has been bringing between $700 & $800 on GB.

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I recall that there were 300 of the PC version made and about 700 with the round barrel.

SAAMI pressure limits for the .40 S&W are 35,000 psi while those for the 10mm are 37,500 psi. I suppose that small difference could affect the revolver's safety margin, but I know of several examples of the 10mm conversion being done with no obvious short-term ill effects. I don't think long term effects have been determined yet. However, I would be suspicious that lengthening the chambers would expose untreated Titanium, and I don't know the effects of that. Aluminium has the characteristic that if new surface is exposed, it oxidizes quickly. But that oxide is stable and no more deterioration takes place. I don't know about Titanium.


Buck

The most credible numbers I've found is 400 PC guns and 300 Non-PC guns. I have one of the latter.

I've bought my moonclips direct from S&W. Also, Rimz makes the easy to use polymer moonclips for the 646.

I've read about a couple of 10mm conversions being attempted but never found any follow up info as to how they came out.

I agree with Revolver King's value estimates.

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With the 10mm conversions. From what I have read is people are not using the ti 646 cylinder but taking a 6 shoot 686 cylinder and having it reamed out to 10 mm. I read that as long as you stay with regular 10 mm factory type loading (not doubletap/buffalo bore) you'll be ok.

That's a new one on me. Supposedly steel cylinders couldn't handle the pressure since the walls would be so thin with .40cal chambers, that's why they went with titanium. If steel couldn't be trusted with .40 I wouldn't want to try 10mm.

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Gentleman,

I appreciate the Input. This gun is the PC model. I probably will sell it in the future. I already own a 610 no-dash 5". I thought it was interesting at the time when I bought it. It is really light! I guess titanium has to many issues to be mainstream. Really hope to convert it to 10mm. That was why I purchased the the extra cylinder and barrel.

If I am not careful I will end on one of those hoarding shows.
I own way too many firearms.

Out Here!

Sorry to dredge up an old thread but I only recently heard of the 646 and it interests me greatly. For one, I have never heard of titanium having a problem with oxygen. My experience has been limited to jewelry and cycling applications so I couldn't tell you about the effects of extreme pressure and temperature. It is way more flexible than steel which might account for some of the sticky extraction issues I've heard about. I won't speculate on if those cylinders could handle chambering for 10mm because I simply don't have adequate data, but I'm not sure why you would do it. I imagine the recoil would be less than pleasant in a revolver that light, maybe concealed carry deer hunting?
That said, if you are ever looking to unburden yourself of that extra cylinder(or for that matter the 646) I would be very interested in "helping" you out.

wish they made some .40 ar brass. The 646 is good size for the cartridge. Something nice about revolvers where the case is short enough for more relable ejection.

Funny I saw your post as I was getting ready to post a for sale post about my 646 and my spare cylinder.... The 646 was bored out for 10mm and I have had no problems with the low pressure 10mm out of it. I had the cylinder fluxed and zero stress cracks....

Just a thought; they built the 610 specifically for the 10mm. I have one with the 3" barrel and the 6" barrel. Also have a non PC 646. I thought that the 646 would make a good 10mm conversion, then I measured the cylinder walls, web between the cylinders, all that stuff. Concluded that it was not worth the risk, as an accident could really ruin my day. Both the 40 and the 10mm are high end pressure max performance rounds. I think that it is best that they be used in guns specifically designed for them.
YMMV................

Funny that I ran across this older thread and after reading all the posts, I thought I would throw out additional food for thought.

As manufactured, the 646 has a 6 shot Titanium cylinder.
The reason for this is the fact that a SS cylinder, as mentioned in a previous post, DOES NOT HAVE the necessary strength due to insufficient wall thichness at the cylinder stops. Since a poster has stated that he's had modifications done and is firing 10mm cartridges and hasn't seen any problems shows it's possible, BUT I don't believe it's wise to do so.
There is also another older thread that mentioned the fact that they were looking at wanting a 646 chambered in 41mag. as a CC weapon. This also CAN'T be done with the "L" frame 6 shot cylinder.

BUT, a very doable method for conversion and workaround the restrictions that a 6 shot "L" frame has, is going to a SS, "NOT" Titanium, 5 shot cylinder that places the cylinder stop notch between the chanbers. On the 40/10mm, you have a .086' chamber wall and with a 41mag. cartridge, the chamber wall is approximately .045"/.046" chamber wall. I'm not qualified to make the determination that this is in fact safe, but when you consider the different loadings and wall thicknesses for a "N" frame 6 shot cylinder, I believe that it is.
In addition, a prime example of a similar undertaken by S&W is the Model 696, "L" frame, 5 shot 44spl.

The one thing that would be required depending on which cartridge was chambered is the 40/10mm would also require NEW moonclips.

I'm currently looking for an available Gunsmithing shop, along with cost that will do a new SS 5 shot 40/10mm cylinder assembly and also moonclips to convert my model 646 for CC carry.
In addition, a 41mag conversion would necessate some barrel work.

If any poster can recommend a gunsmithing shop that they have dealt with, would be appreciated.

baldeagle8888

Please BUMP TO TOP

baldeagle8888

Bought this LNIB for $550 and never shot it. Sold it for $700. Now I am sorry I did

baldeagle8888 - Hamilton Bowen could do that kind of work for you - + Bowen Classic Arms + Home - be sure to bring a blank check.

You might also consider Clements Custom Guns, they do a .40/10mm GP100 conversion www.clementscustomguns.com/rugerdarevolvers.html (I know, I know, it's not a S&W, whatever). I have considered having this done to a 3" GP100 just because they're so cool, but I don't have any .40s or 10mms (sold my 646 last year) and don't really want to invest in another caliber.

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