Ruger used(uses) a .22Mag bore spec bbl on their .22lr/22mag convertible revolvers. I think Colt did the same.
So when using the .22LR cylinder the bullets are going down a slightly oversize bore. But the results are not all that bad and the revolvers are not sold as Target Accuracy jobs anyway.

The 'one caliber' only editions of the Single Six used to have a bbl that matched the caliber, instead of using a one-size-fits-all approach.
I don't know if they bother to do that anymore.