I'm not the best S&W guy but the 61 was the "Escort" a semi .22LR. The 651 is probably the J frame 22WMR you are thinking about.
One of my good shooting friend's is a S&W guy and he has a 651 and an 18. I sold him a 48 years ago (blued K frame .22WMR) and I have a 648, the stainless full underlug version of the 48.
Hard to beat the modern .22LR semiautos for accuracy though.