Remove 38/357 cyl, replace with 38+P?

[snubbert]

Despite my preference for older post-war Smiths, if the current 640 Pro Series was 38 spl only, I'd likely own it. All steel J-frame, good sights, overbuilt frame for 38 spl/+P. I'm aware that you can shoot 38 spl in the 357 cylinder, etc. More interested in what it would take to do this:

Is it possible to (successfully and safely) put a steel 38 spl-only cylinder from another modern J frame (such as the 642) into the 640 Pro Series?

1. If the entire swing-out assembly is swapped (including crane, extractor, etc. - everything that comes off when you remove that one screw on the frame), would it be easier than swapping just the cylinder?
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2. What sort of fitment or other problems might come up?
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3. What model might be a suitable donor, in terms of ease of swap?
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4. On an alloy frame with steel cylinder, is the crane also alloy, or is that steel?
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5. Legal issues?​

 

[Zipdog]

Why not get a machinist to make you some sleeves to press into the cylinder you have to prevent .357 from going in all the way? Some armchair expert will tell you it can't be done. They'll be along soon enough.

 

[colt_saa]

Almost any project is possible if you throw enough cash at it.

You only need a new cylinder assembly.

You could go with a Titanium cylinder and save some weight.

 

[armorer951]

I believe the 38 only cylinder would be shorter in overall length, which would necessitate having the barrel set back....or a new barrel with the proper length thread/forcing cone area fitted. Other issues also, like the extractor rod, etc.

 

[Muss Muggins]

Buy a different gun . . .

 

[*chris*]

.38 only,

I assume you mean 38 Special (357 caliber) , not .38 caliber right?

The biggest issue is lock-up and timing with the ratchet and hand which would probably require a gunsmith.

I have to ask why? With a snub nose, you are not going to see any accuracy difference.

If you want to prevent 357 mags from chambering, shoot a bunch of 38 special and don't clean the cylinders, they will carbon up preventing 357 mag from chambering in no time.

Chris

 

[F75gunslinger]

The 640 is an all stainless gun. The frame, cylinder , and crane are all stainless steel. It is built on the J magnum frame, so any .38 special cylinder you try to use will be too short, causing you to have to set the barrel back to have the proper cylinder/barrel gap.

I think thet the cost for smithing work would be prohibitive for what you're wanting.

If all you want is a 38 special chambered 640, look on gunbroker. They did make them, and they can be found. Being all stainless they'll easily handle +p loads.

The sights won't be the same as the pro model , but would fit your chamber requirements. OR, just buy the 640 Pro and shoot 38 specials in it exclusively. It seems to me that you're making up an issue that is more or less a moot point.

 

[snubbert]

I assume you mean 38 Special (357 caliber) , not .38 caliber right?

Correct! Edited my original post to fix that.

The biggest issue is lock-up and timing with the ratchet and hand which would probably require a gunsmith.

If you want to prevent 357 mags from chambering, shoot a bunch of 38 special and don't clean the cylinders, they will carbon up preventing 357 mag from chambering in no time.

Now that's not a bad idea...

 

[snubbert]

You all make good points and in the time it took for me to search gunbroker etc and then come back to the forum to check on replies, I (and you) have already talked me out of it, and into something made specifically for the 38 spl such as the 640 or 649 in the non-magnum frame. Thanks all.

 

[k22fan]

I'm a slow writer so this is mostly redundant and I read that you've already decided against it, but if you need more convincing, read on.

< 1. The SCSW writes the original Model 60's nominal 1.53" cylinder length was increased to 1.60" in the J Magnum frame. I do not know if some J Magnum frames were completed as .38 Specials with the longer cylinder. Whether or not longer .38 Special cylinders exist is the first thing you need to investigate.

1. Yokes are not interchangeable between identical S&W revolvers. Like side plates yokes are fitted to individual frames then all three are stamped with an assembly number so they wind up back together after what ever manufacturing steps separate them. You can get lucky but the random yokes I've tried dropping in have all not fit.

2. If you are changing cylinders of the same basic length within the same model and are not lucky any or all of these may require work. If the replacement cylinder has excess end shake then you add end shake washers. If the yoke tube is too long for your drop in cylinder then you shorted the yoke and add end shake washers to your original cylinder. If the flash gap is excessive with your new cylinder then you set the barrel back a revolution which involves all the tools and skill for fitting a new barrel. Figure $100 to $150 worth of gunsmithing. Additionally, if you want to continue using the original cylinder then you face off the front of it in a lathe to make it as short as the new cylinder. If the flash gap with the new cylinder is too small or the cylinder won't close then you're a lucky boy because for both cylinders to work you only have to shorten the front of the new cylinder.

Model 60 ratchet teeth have not always had the same shape. One of the used Model 60 cylinders I tried had odd shaped ratchet teeth that gave it no hope of working in my revolver. Even if your new ratchet teeth have the same basic shape as the original ratchet you might still need a hand with a different thickness. Also the surface finish has changed over the years. Originally stainless S&Ws were finished to a surface that could be duplicated with the right grit of Scotch Brite pad. During the 1990s they changed to tumbling the parts of most revolvers but some production runs were bead blasted.

3. & 4. I leave for a member who knows J frames better than I.

Post 5. in the Concealed Carry sub-forum for lively disagreement. I would not worry about it.

 

[Allen-frame]

The 640-1 and the 640-2 are built on the J Magnum frame . The cylinder window is sized for the larger 357 Magnum cylinder.

The 640-2 is a 38 Special only gun., I have one.

I have fitted a 357 cylinder to it so I have both 38 and 357 cylinders.

http://smith-wessonforum.com/s-w-re...really-need-more-than-38-special-j-frame.html



Allen Frame

 

[k22fan]

Since some 4" Model 63 .22 LRs were built on J magnum frames I am not surprised that some J magnum frames were assembled as .38 Specials. Allen, thanks for the link.

 

[H Richard]

This is one of the reasons why I recently purchased a 640 (38 Spec "only") for my own use. It will handle +P, and it isn't as big as the stretched frame of the .357 640-1.

 

[WC145]

All J frames since about 1996 are built on the J magnum frame so any .38spl only cylinder from a J magnum framed gun will fit the 640 Pro Series - 642, 442, 360J, etc..

The easiest way to do it is to just replace the cylinder, you might be able to take the ejector star and ejector rod and swap them in the new cylinder and make it work. Or, as has been pointed out, a complete cylinder assembly from another gun may drop in and work but more than likely the project will require gunsmithing.

Why would there be legal issues? What law could you possibly be breaking?

The bigger question is why bother with such a project at all? Simplest, easiest, least expensive, and most sensible solution is to just not use .357 magnum ammunition. You're not going to gain anything by changing to a .38spl cylinder. The gun will not work better, it will not be any more accurate, and, unless you have S&W do it (assuming they would) the gun will no longer be covered by the warranty.

If you absolutely must have a .38spl 640 hunt one up and buy it, that's a better fix.