I know this has been discussed here and there, but I cant seem to find an in depth description. For those of you who have had a 38/357 cylinder reamed to 9mm, can you give me a description of you accuracy, maybe even pictures? Ive read that accuracy is not as good or that it shoots a little low etc. Can anyone be a little more detailed?

The 38 Bullet is larger, but the casing of the 9mm is larger.
A 38 casing has a diameter of 3.79.
A 9mm casing has a diameter of 3.91 at its base and 3.81 at its neck, so the cylinder needs to be reamed for the 9mm cartridge to fit.

This was posted a short time ago. May help.

My Model 66-2 Just Back From TK Customs

Thanks KLYDE, I can live with that.

You might asked around on a Ruger Blackhawk forum. Ruger makes, or made, a .357 BH version that had a second cylinder in 9mm. It was around for a looooong time so I know a bunch had to of been made. To a 0.355" bullet a 0.357" barrel is a 0.357" barrel.

__________________
~ S&W aficionado in training ~

My three 637-2 9mm conversions did not lose any detectable accuracy
.

I have been shooting 9MM cartridges in converted 357 Magnum revolvers for decades. My favorite being this 8 shot 627 that I have a second cylinder set up for 9x23 Winchester
All of mine shoot just fine.

However there is a reason that there are two completely different experiences and why both are 100% correct

Accuracy is mostly a function of proper bullet spin.

Bullet spin is caused by the rifling engaging the projectile

Most people forget that there is both a land and a groove diameter involved when they talk about bore diameter. What is actually measured when folks slug a barrel is the groove diameter.

The difference between the land and the groove is the depth of the rifling, the part that actually engages the projectile thus causing spin.

This difference is somewhere around .008" - .013" depending on the type of rifling and who did it
Jacketed, plated and coated 9MM projectiles measure anywhere from .355" - "3565" depending on the manufacturer. There is still plenty of projectile for the lands to grab onto and get spin even in a .357" barrel.

I have been shooting jacketed 9MM projectiles through many different .357" barrels for several decades now.

BTW, most 38 Super shooters (.365" bore) have been loading 9MM projectiles for more than half a century now, but this discussion never comes up. Heck, most of them do not even realize they are doing it

The accuracy exception/complaints from shooting 9MM ammunition in a .357 bore comes when we are discussing lead projectiles.

For least amount of leading and therefore best accuracy the lead projectile needs to properly fit the cylinder throat/barrel it is being fired from.

So, yes shooting lead projectiles sized .355 in a .357 bore will usually lead rapidly and accuracy will often be sub-standard