I am looking for replacement grips and backstrap for my S&W 669 Series. I have tried Uncle Mikes grips and they were a little too snug on the inside for the mag to slide out on it's own upon release. I had to physically pull the mag out of the frame.

Any first hand grip experience on a good replacement?

You must not have installed the UM's correctly.....I have them on my 669 CCW and they are great grips....no mag issues.