This is a revolver that ships with both a .357  and a 9mm cylinder. I would like to know how well they shoot with both rounds. Does a 9mm Para use the exact same bore size as a .357 Mag?

Thanks

Basically, yes.....the bullet size is the same......what is your concern?

Well, I also have a cowboy revolver in .22 cal which has swappable cylinders to accomodate both 22LR and 22WMR, however, LR is .221 and WMR is .224. It is generally known that the performance of the 22LR in these guns suffers. Thats OK for a plinker, but if I am going to get the big .357 / 9mm, I want to know that both rounds are the same size, and thus will shoot accurately through the same barrel.

Thanks

Suggest you go to some of the bullet makers websites and dig up some specs....if memory serves..the 9 is technically a few thousands bigger.....but i`m not sure if you can`t get both in something like 377.....I have the 38 convertible and 45 convertible.....can`t tell you that I ever noticed a serious difference with either...but I was never benching or score shooting either.....just plinkers...

I personally avoid any pistol that isn't a true dual-caliber gun.  Example would be shooting .38 out of a .357 mag pistol.  I think that there are some Blackhawks that allow both a .45LC and a .45ACP with a swap of cylinders (don't quote me).

The 9mm is slightly different in diameter, so n doubt you are going to suffer accuracy in either your .357 or 9mm chambering.  Might have to do a slight elevation adjustment to the rear sight as well (who knows).

I have found out that there is indeed a difference in diameter between the 9mm and .357 Mag rounds.

The 9mm is .355 jacketed or .356 cast.
The .357 Mag is .357 jacketed or .358 cast.

Is that 1-2 thousandths going to make a big difference when shooting a 9mm through a .357 barrel?

Here is the real poop.  As mentioned previously 9mm is .355" dia.   38 spl and 357 mag are both .357" dia.  I had a Blackhawk 9/357 convertible, it was very sloppy and shot both rounds the same, that is rather poorly. Sold it cheap. Some are nice and tight and they do shoot rather well (in both calibers).  If you like single-action revolvers (I do!) and already shoot a 9mm pistol, I think ir would be a great piece.  You can shoot full power 357 Magnums for hunting or whatever, 38 specials and 9MM for plinking, small game, etc.  Just handle the revolvef first.  If there is more than minute slop in the cylinder to frame fit (around the base pin) turn it down. JUst check it out good first new or used.  I have a 1957 Flattop in 357 that has seen many thousand rounds and still shoots decent.  The things seem to last forever.