Expanded Chambers?

That for-sale cylinder is listed for 357 mag (and 38/+P). It will be longer than your original 38 only cylinder. Even if your gunsmith could fit it it's chambered in 357 making it able to chamber them - this is very likely to be very unsafe in your 38 only 640 no dash frame.

Related story that may or may not be helpful. I double charged my S&W 610 many years ago. I happened with one of my first batches of ammo from a progressive reloader as I was learning to use a friends press and I somehow stuffed a double charger of Titegroup in a 40S&W case. 9.0 grs of Titegroup under a 180gr bullet is a wee bit hot. Quickloads predicts between 80 and 90 ksi The gun went bang and locked up solid. I had to pound the cylinder open and use a punch and hammer to get the case out of the cylinder. The case came out in two nearly three pieces. The front of the case burned though were the web tappers down to the wall, the case head nearly separated from the web in a rupture that went almost fully around the extractor groove.

Surprisingly there was no obvious damage other than a few minor scratches in the recoil shield from the moonclip getting deformed. It was only after getting some good calipers on the cylinder did I found the chamber that had experience the double charge was stretched about .010 larger in diameter but only in the radial direction (relative to the cylinder as a whole) not the tangential direction and only to a depth of about .10 inches.

Out of an abundance of caution I sent it back to S&W for a safety check they offered at the time from the service department. In a letter I included with the guns return I fully disclose that the gun was bought used and that I had fired what I highly suspected was a double charge or reloaded ammo in the revolver. I even include pictures of the revolver with the mangled case and moonclip before and after I manage to extract it from the cylinder. I told them to fix anything they thought needed fixing and I would be happy to pay for the work. S&W looked over the revolver, replaced the cylinder latch spring and fitted a new cylinder latch and sent it back to me. The only money I was out was the cost to ship it to them, they did not charger me for the work or return shipping. I had the revolver back in 8-days.

I went on to shoot probably 20,000 more rounds through that revolver in USPSA competition over the next 4+ years and then when I retired it from competion I have used it as a hunting revolver with some fairly stout 10mm reloads.

A picture of fired cases and their dimensions from all five chambers may help figure out what and where the factory saw their concerns. With 6-shot K-L-N frames its usually the bolt notches that are the first weak spots in the cylinder, the steel in those notches can fail with hot enough rounds before the whole cylinder goes.

In 5-shot .38 -.357 J frames the offset notches pretty much take that weak spot away, so we can only guess what it could be. (I am thinking it is one or two of the cylinder chambers that have gone out of spec.)

If you have some pics, post them .

Stay safe.

Just curious since you have owned it so long, any idea what type of round count and what type of ammo has been run thru it. My 640 is of 1992 vintage and has served me thru a career and the years to follow shooting nothing but +P. It was in fact the reason my Dept authorized it as it was rated for +P. Thanks!

I will give you a for instance in my revolvers round count as it’s lineage is similar to yours. Initial purchase and training around 1000 rounds Federal Nyclad 158 SWC+P. Subsequent Bi-Yearly Qualification 100 Rounds a year at minimum Federal158 SWC, 158 SWC-HP and mostly Speer 135 HP Short Barrel all +P (this is a very conservative number and does not include individual training courses along the way all with authorized ammo and always +P) But let’s say another 3000. Then we figure my own practice, always with authorized ammo (it was free) a few thousand more. I am going to say the gun has a a very conservative 5000+ +P factory rounds and other than a smooth light trigger (got a sly eye by a range officer or two) the gun is factory tight!

Nothing is worth getting hurt over but I am having a hard time believing that factory +P would fatigue the cylinder. The gun as I am lead to believe was marketed to Law Enforcement specifically for the reason of shooting +P and dare I say +P+.

YMMV but my take away from this is S&W ain't what they used to be. First they tell you the cylinder is "swollen", then they tell you they can't find a replacement cylinder. Can't find one? They're the manufacturer for goodness sake. What a load of the smelly stuff that come from the back end of a male bovine.

Dave

@wcwhitey May I ask what pocket holster is in your picture? It looks functional and appealing.

The original run of 640's were marked inside the window "Tested +P+. I shot a thousand +P+ thru mine with no ill effects. I shot some early Super Vel and Cor Bon that was hotter than a 2 dollar pistol.

Mikey5oh said:

Safe to say at least 1000 rounds through it.
It was my back up/off duty weapon.

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1,000 rounds is not much at all. Pretty sure I shot that many practicing with my 638 the first year I had it

Jonesy814 said:

1,000 rounds is not much at all. Pretty sure I shot that many practicing with my 638 the first year I had it

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Not if the rounds used are at pressures less than, or equal, to the design pressures of the firearm.

I remember the call in show, Car Talk on NPR. Click and Clack had a military caller from Iraq who wanted to know if there was a special grease that would extend the lifetime of ball joints. Turns out they were replacing the ball joints of HMMWV's every couple of weeks. A bit more probbing by the Tappit brothers found the weight on the HMMWV's was several tons (if not more) over gross! The Army had never intended the HMMWV to be an Armored vehicle, and yet that is what the Army was doing to give the crew a chance of survival in the shooting gallery called Iraqi.

Ball joints ought to last 200,000 miles if well greased and if the vehicle is not heavily loaded. They will go in 100,000 miles if not constantly greased and if a lot of weight is on the wheels.

If a pistol is not rated for +P loads, a 1000 rounds would be an over load, and you would expect the pistol to be beat out of time, and the cylinders to stretch past yield.

And, I am going to claim, stay away from pressure maximums. Smith and Wesson wants to sell you firearms, so they will not challenge your fantasies, or tell you that your desires have no basis in physical reality. And this is because, delusional people don't want to hear it, and then they will buy the Tropical Jack Gun Company pistol, guaranteed to function with mini nukes. Except the Tropical Jack company is an LLC, and will go away when too many lawsuits are pressed. Smith and Wesson knows, the people who want Buffalo stomping loads will probably only fire 50 rounds, and then the pistol will be put up. People who fired tens of thousands of rounds figure out, pressure is not their friend, because they start to experience, or see, fatigue failures.

Slamfire said:

I remember the call in show, Car Talk on NPR.

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Awesome show. Probably one of the best ever on radio.

Slamfire said:

I remember the call in show, Car Talk on NPR.

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One of the many programs that made NPR worth tuning into, that pretty much came to an end a decade plus years ago..