As others noted it should be fine. Maybe 25 years ago I wandered in to the local parts shop and low and behold in a red Ruger cylinder bag was a NOS S&W K frame 22 WRM cylinder. Had it fitted (minor, 5 minutes file time) to my pre-18 and it worked like a charm. All these years later still shoots great with either the original 22LR cylinder or the 22WRM. Accuracy seems the same with both. Enjoy it.

Jeff
SWCA #1457