You removed the pin on the bottom, right?
What part # were you using?
OP - they sure look like N frame grips to me.
It should fit. Maybe some excess material on the inside, as jbtrucker suggests.It is the Pachmayr Diamond Pro Comfort Fit Handgun Grip S&W "K&L" Frame Round Butt Item #02479
I have 3 different N Frames wearing Diamond Pros. Never had an installation issue, and the fit is perfect. By far my favorite rubber grips.