Magnum cylinder for Single-Six

[ArchAngelCD]

Is it possible to buy a .22. Magnum cylinder for my Single-Six or does it have to be fitted to the gun by Ruger. I read somewhere Ruger won't sell you one unless the serial number tells them the gun originally came with both cylinders, true?

Thanks for any info you can provide.

 

[Tallball]

You can buy used ones on ebay. I've always read that they might or might not need some hand fitting. Mine didn't.