for 357 revolver is 358 diamer or 359 diameter best?

[blasternank]

my 627's (357 mag) and my 929 (9mm) barrels both measure at .357 diameter. Would it be best to get a .358 or .359 diameter molds?

[onelight]

What size is a snug push through your cylinder ?

[Conditor22]

my guns like .358

[JWFilips]

For cast I like .359" but not hard alloy! Maybe COWW or COWW and Pure.
Fat bullets have always shot better for me

[blasternank]

What size is a snug push through your cylinder ?

357 is the measurement when done with micrometers

[JonB_in_Glencoe]

359 is best, if it chambers.

[Outpost75]

Micrometer cannot measure small round holes because the knife edges bridge across the radius and give a smaller number. Best to use gage pins, expandable ball mic or drive soft, pure lead ball through cylinder throats and measure. That being said the great majority of modern S&W revolvers will pin .3585-.3588 and either a,.358 or .359 bullet will be accurate. Ideal fit is to be able to push bullet through throats by hand pressure only with slight felt resistance.

[Wayne Smith]

So get a .359 mold and a .358 size die and you are set.

[tazman]

Micrometer cannot measure small round holes because the knife edges bridge across the radius and give a smaller number. Best to use gage pins, expandable ball mic or drive soft, pure lead ball through cylinder throats and measure. That being said the great majority of modern S&W revolvers will pin .3585-.3588 and either a,.358 or .359 bullet will be accurate. Ideal fit is to be able to push bullet through throats by hand pressure only with slight felt resistance.

^^^^^^^This.
The cylinder throats determine the size the boolits need to be unless they are smaller than the groove diameter of the barrel. In that case, the throats need to be reamed to the proper size.
Outpost is also correct about the normal size for S&W 38/357 cylinder throats.
Your 929 is a different animal. I have one. Mine has a groove diameter of .355 which is nominal for 9mm. The cylinder throats measure .357 on mine. I run .357 boolits in it and it works fine. The chambers will accept larger boolits but it isn't necessary because the throats will size the boolits down anyway. Accuracy was not improved by larger diameter.
I normally size most of my 38 cal boolits at .357. I am not a good enough shot to make use of any accuracy improvement from a larger boolit. Mine may be bumping up to throat size anyway.
I have no issues with leading with any of the boolits I shoot in multiple revolvers. I lube with White Label NRA 50-50 using a Lyman lubrisizer.

[DougGuy]

It is a rare cylinder indeed that will take a .3585" gage pin in my experience .357" in a S&W is almost always a go where .358" is normally a no go. Not saying this for the sake of argument, but hundreds of S&W cylinders measured and reamed or honed over the years. If they were already .358" I wouldn't have been resizing them for years.

If you can get a .358" to chamber, this would be the most popular size for 38/357 revolvers. If you cannot chamber a .358" I would have the cylinder throats honed so that you can.

[tazman]

It is a rare cylinder indeed that will take a .3585" gage pin in my experience .357" in a S&W is almost always a go where .358" is normally a no go. Not saying this for the sake of argument, but hundreds of S&W cylinders measured and reamed or honed over the years. If they were already .358" I wouldn't have been resizing them for years.

If you can get a .358" to chamber, this would be the most popular size for 38/357 revolvers. If you cannot chamber a .358" I would have the cylinder throats honed so that you can.

In support of this, I own a couple of revolvers that measure less than .357 in the cylinder throats. In my case, the groove diameter is small enough that it isn't an issue.
Throats at .356 with groove diameter at .355 works fine.
All the dimensions need to form a funnel going forward. If this is the case, no work is needed and nearly any normal diameter boolit will work.

As an example, I own a Model 60 S&W. Early model in 38 Special. Chambers will accept boolits up to .359 but the throats are .3565(I pushed a lead ball through the cylinder and measured it with a micrometer). Groove diameter is .355 or slightly less. Slugs from the barrel fall through the cylinder easily.