First let me say that I am new to posting on GT and am posting here because my question is specific to the g21sf and thought this would give me an informed audience. However, I am not a numbered member of this "club" so if that makes a difference please move this post to where it should be thanks. Now to the question... How do I know if I have a g21sf that has a defective mag release? I recently purchased a g21sf, ambi mag release, w/ glock rail (have not been to the range yet to break er in either). I was on today and was reading about a group of you who have had issues with the mag catch or mag release of the 21sf ambi version. It got me wondering. Does mine have an issue? How would I know if it had an issue? I did some mag drops w/ loaded and unloaded mags using the left & right side mag releases, seems fine. Listened to the mag as it clicked in and only could hear one distinct click, no double clicking as I read about. So, how does one know if they need to have their's looked at? Mine has a Mxxxx0 SN and a spent shell casing dated 01/15/09. Any ideas?