Ream out 38 to 357? (J-frame)

Don’t do it

Anchorite said:

Because ……
I’ll blow my hand off?
I’ll ruin the value?

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.357 in a J-frame will hurt. Plus, if the J-frame wasn't designed to handle .357, you very well could blow your hand off. If you really want to re-chamber it to another caliber, I suggest 9mm so you can use full moon clips to allow for really fast reloads.

I though the 640 was 357 Magnum from the factory? Do you have a 642?

Contact Mark Hartshorne and ask him. He's the best revolver 'smith I know. He'll know the answer.

Metallurgy ???
Could there be different heat treatments for the different pistols designed for different cartridges. I don't know just wondering. For me I wouldn't do it. I'm not sure how much benefit I'd get from a .357 out of a 1 7/8 inch barrel. Is there enough performance benefit when weighed against the increase in recoil and all that comes with that. I don't think it's for me, but each to his own.

Might be cheaper to get a .357 than do the ream. Plus there would not ever be the danger of over-pressure. If (heaven forbid) a hand is lost to the "ream job" how could one explain it to friends and next of kin?

Anchorite said:

Mines a 38. NOT a 357, which is why I posted this question in the first place. Why can’t I punch the cylinder out? Are they not equal in size? (640 and 640 in 357)

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Same OD, shorter length. There were a number of early Ruger SP101 .38s rechambered to Magnum but they were limited to the shorter OAL ammo. The 640 Special would be the same.

Same steel and heat treat? Who knows, Smith won't tell you.

I doubt you will find a reputable gunsmith who will rechamber it, which may seem strange, the 9mm conversions are not much lower pressure.

Anchorite said:

I just never shoot my 640 b/c it’s a plain-jane 38 Special.

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I'm just the opposite; when I heard they were magnumizing the steel J frames, I hurried to get one of the last 640 Specials. Kicks bad enough anyhow.

The original release M640 were marked TESTED FOR +P+ and the serial number were CEN****. Follow on production eliminated TESTED FOR +P+ as there was no industry standard pressure rating for +P+. The grips were smooth wood reddish in color.

If you do ream it you will likely be limited to 110 gr (just like the early Ruger SP-101s are) as S&W cylinders are caliber specific (unless they have changes policy). 38SP/44SP are shorter than 357M/44M with correspondingly longer barrels that extend further into the frame window. There's also this - While I have seen a very few K-frame guns with frames cracked at the barrel thread, I've seen quite a few J-frame guns cracked there. There's not nearly as much meat there on the J-frame as on the larger guns. Stand to reason that the 357 is going to put a bunch more stress on the gun, significantly reducing its lifespan.

Midway once sold a 357 mag cylender for doing exactly that.

Hangingrock said:

The original release M640 were marked TESTED FOR +P+ and the serial number were CEN****. Follow on production eliminated TESTED FOR +P+ as there was no industry standard pressure rating for +P+. The grips were smooth wood reddish in color.

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There still isn't an industry standard for +P+.

+P loadings generally produce about 10% more pressure than non +P ammunition, but this isn't a truism all the time, nor is it a definition. It would be better put that +P is more than standard, up to approximately 10% over nominal pressures.

+P+ isn't a SAAMI defined standard at all and falls under an even broader generalization. It's generally considered to be about 10% to 15% more pressure than +P. However, pretty much anything loaded beyond +P all the way up to, but just shy of, proof pressures is considered +P+.

Which makes "TESTED FOR +P+" a dubious marking, in my opinion, as proof testing would technically meet that standard. However, proof testing is typically a one-time firing at proof pressures (per chamber...so a 6-shot revolver would require 6 proof shots, one for each chamber).

+P+ is pretty much whatever the manufacturer says it is...and good luck getting meaningful details on this from the manufacturer(s).

I think it is a bad idea. Too many known unknowns.

Is the metallurgy the same?

Are the heat treatments the same.

Are the chamber, bore, forcing cones the same?

There are lots of 357 snubbies. And I don't own a one because the muzzle blast and recoil is horrible. I like my snubbies as 38 Specials.

But we were going to hold your beer.

Hangingrock said:

The original release M640 were marked TESTED FOR +P+ and the serial number were CEN****. Follow on production eliminated TESTED FOR +P+ as there was no industry standard pressure rating for +P+. The grips were smooth wood reddish in color.

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The grips must’ve changed, too, as my 1991-vintage 640 .38 Spl. with the 1 7/8” barrel didn’t have grips that color.

As for the OP, good idea to leave the vintage .38 a .38. The .357 versions were strengthened for the .357 cartridge over the original .38’s. Pick up a .357 version… and in all honesty you’ll probably be shooting .38’s in it before long .

Stay safe.

I have snubs in 357 and 44mag, I shoot specials in both...

I have a 640 357, for my carry. I practice with 38 specials. I carry with 357 or 38's. All of the above advice is good. Leave it alone, the J frame is not that strong. Proper bullets are good enough for 38's self-defense. Shot placement is everything, Practice with 38's is enjoyable. Paper does not lie. Practice ,Practice

Anchorite said:

I have a 640 (38S), does anyone know if it’s possible to have the cylinder punched out to 357

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38 spec - 17,000 psi
357 mag- 35,000 psi
9mm luger- 35,000 psi

Cylinders are heat treated or use differrnt steel as pressures increase. Ask S&W, they are the only ones that will know.
The Ruger 454 cylinders have been proofed at 90,000 psi.

My guess, bad idea to modify for 357 or 9mm. The moon clicks are a pain.

Once upon a time Winchester produced a law enforcement .38 spl loading designated +p+. While there was not/is not an industry standard for +p+ Winchester did have a standard for what they produced. I think that they set the pressure ceiling at 24,600 cup but I don't remember with absolute certainty. In any case S&W did have a reference for what they were approving. As for reaming to .357, I would not do so.

Reaming GP100s and SP101 from 38spl to 357 is very common. There's no difference between Ruger 38spl and 357 cylinders other than the final finishing of the cylinder. Are S&W not the same? Seems like a lot of work and risk not to use the same material no matter the final reaming. A mix-up using 38spl cylinder and accidentally reaming to 357 would be exciting in a negative way.