Hey all....About a year ago I purchased a used New Model Blackhawk.  The gun came with only one cylinder in a .357
Now for kicks, I want to find a 9mm cylinder for this thing.  I realize the matching of numbers to insure timing but I'm pretty sure its near impossible to find a match.  How can I go about this??
Are the last three digits of the serial number part of a 'lot' or were they all one off's that matched the pistols when manufactured?
I hope these arent stupid questions and thanks.

Numbers have nothing to do with cylinder fit.
The cylinders are usually numbered simply to insure THAT cylinder stays with THAT gun.
Revolver cylinder MUST be individually fitted to a specific gun.

I'd be talking to Ruger about it, since they still make their .357/9mm convertible Blackhawk.

Since they currently make 9mm cylinders, the charge to have a new one fitted to your gun should be fairly easy and reasonable.
They know more about it than anyone, and their pricing and turn-around will be better than any custom 'smith.

www.ruger.com/

A phone call might get the info faster.

someone asked a similiar question on another forum.They tried to just buy the 9mm cylinder from ruger but they wouldn't sell him one because they said it needed to be fitted to the gun.He didn't say if they would fit it for him though.I have thier 357/9mm convertable and its a pretty cool gun to shoot.Just roll out the one cylinder and pop the other in.I know I have seen 22 and 22mag cylinders for sale by themselves but I have never seen a 9mm one.

I used to have one. The factory 9mm never shot very well. I think I was able to get lead reloads to shoot ok but execpt for ammo interchangeability (SHTF yada yada yada) what's the point? Times are gonna be pretty rough if you can't find .357 or 38 of some kind . I sent my cylinder off to some place in Ca. that drilled it out to 44 Bain and Davis.This is a  44 mag necked down to .357. Kind of goofy . You waste quite of bit of brass necking them down,have to neck reem and trim. Since it is a bottleneck Cartridge you have to watch out for setback and so forth. Good news is you can get pretty high velocity but with a ruger blackhawk you can wip up some fairly stiff reloads with just the .357 case.
My point is although the 9mm cylinder is a interesting toy you might think of putting the money you will spend towards a good used 9mm.
I think by the time you buy the cylinder,have it fitted,and pay for the shipping to have it fitted you are going to have $125-$150 into it. Another thing to think on if your gun is the old model is that ruger will only do work on it if you have them put the transfer bar unit in it. This work is free (I believe) but can affect a otherwise fine trigger pull .

theres 2-9mm blackhawk cylinders on ebay right now

i have a new model convertible and it is a lot of fun for the sole reason that single action shooting is enjoyable and 9mm is much cheaper than even .38spl.  and that is the main reason why i bought that revolver.  if you reload then there is no real point to getting the 9mm cylinder because then you can just load some lighter loads instead of shooting full house .357mag all the time.

Quoted: theres 2-9mm blackhawk cylinders on ebay right now

THEY WON'T WORK.  
Revolver cylinders MUST be individually fitted to a specific gun.
Revolver cylinders, and most other revolver parts are NOT "drop-in".

Many parts for an automatic can be dropped in with little or no fitting.
Revolvers are different.  They're hand fitted.

Just wanna thank all you guys for the input.  I called Ruger, here's the scoop:  Ship them the gun with the .357 cylinder plus $106.75, this covers 56.75 for the 9mm cylinder, $20.00 labor and $30.00 return shipping.  
They do the fitting and timing and send it back.  Sounds really reasonable to me.  I might just do it.
Thanks again....K

thats not a bad price if you really want one.Beats buying a whole new gun.And the cylinders on ebay would still had to be fitted by a qualified smith.I guess I left that part out of my last post.

i wonder if this would also work for my .357mag Vaquero?

Quoted: i wonder if this would also work for my .357mag Vaquero?

in theory i would think so.  i don't knwo why they don't just sell a convertible vaquero though.