My Blackhawk is a .357 only, but here is a link that to another forum that has some good info:
There is also a lot of great info at
I also have a Ruger Single Six SA revolver. It comes with a cylinder for .22LR and one for .22WMR. The same question has been asked about this gun since the WMR bullet is .002" larger than a LR. I am sure that some people will tell you the LR's are not as accurate as a WMR round because the barrel has to accommodate the larger of the two rounds. I am not a competitive shooter and do not require something hyper-accurate so I personally can't tell any difference. I generally use good ol' Federals from Wal-Mart, so this is probably going to have a greater effect on accuracy than shooting them through a larger barrel.
Bottom line, both guns are great fun to shoot. I only wish I could find more .357 magnums rounds and not have to mortgage the house!