Can one take a 38 spl cylinder and make it so it can shoot 9mm with moon clips. If this conversion is feasable, will the cylinder still be able to shoot 38's or will it forever be dedicated to 9mm

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Forum consigliere

Sure. This "conversion" is possible. See info here:

My 9mm 360J is now a convertible!

9mm conversion

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Ret. LE, FA Instr, S&W Armorer

In the old and older revolver sub-forums members continually post that WW II British .38 S&W cylinders converted to .38 Special by reaming them deeper make the .38 Special cases swell so bad that those revolvers should be avoided and have little value. A cylinder reamed to accept 9 mm makes .38 Special brass swell just as bad. Also making the 9 mm bullet pass unsupported through the .38 Special chamber before entering a too loose chamber throat then a too small bore is not going to improve accuracy. However, I have no doubt the 9mm bullets will still be accurate enough to satisfy a 5 yard expert.

BTW, S&W extractor rods are not strong enough to extract 5 steel 9 mm cases at once so you will not be able to use the least expensive 9 mm cartridges.

How is a .357 bore too small for a .355 9mm bullet?

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protocalldesign.com

How is a .357 bore too small for a .355 9mm bullet?

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protocalldesign.com

I’m also sure that it’s possible and viable for modern guns but I’ll be the first to mention that it needs to be mentioned () that 9mm runs nearly twice the pressure of .38 Special.

Keep that in mind for old guns or shoddy imports.

You can have the rear cyl face cut for moon clips, no problem.

But I would not ream the chambers for 9mm, I'd hone the rear of the chambers just enough to accept the 9mm cases. Then they won't be unduly oversize for 38s.

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Jim
S&WCA #819

Better yet would be to buy another cylinder to modify to 9MM and get it fit to the frame of your gun. That is basically what Ruger did with the convertible Blackhawks. One cylinder for 38/357 and another for 9 MM.

While the European philosophy has been to let bullet metal displaced by the lands fill grooves that are over bullet diameter Americans have traditionally pursued best accuracy by firing bullets that start at groove diameter or in the case of cast bullets a little over groove diameter. I only wrote that the conversion is not going to improve accuracy. If you have no interest in getting the best accuracy out of your guns then we have little common ground for discussion.

9 MM Blackhawks infamously do not get the best accuracy with lead bullets. That can be improved by reaming their 9 MM throats then reloading 9 MM cases with .38 bullets.

I created a .38 Special / 9 mm convertible by having a Model 60 .38 cylinder fitted to my Model 940 9 mm. It is not as easy a job as members imply. S&W does not intend the cylinders of even consecutive serial numbered revolvers coming off the line one after another to be interchangeable. If the barrel has to be set back to reduce B/C gap with one cylinder then the other cylinder has to be faced off in a lathe etc., etc.