My Model 60 did the same thing as your friend's Model 60, I'm 99% sure it was the IL. I say that because the flag was partially up and unlocking it with the key "solved" the problem. To get it unlocked I had to thumb the hammer back slightly to take pressure off the flag while manipulating the key. The gun was purchased as a concealed carry weapon, but suddenly it was no longer trustworthy. The '60 and my 642 received a "lockectomy" and both have performed perfectly ever since. The only S&W revolvers I will consider buying any more are pre-lock models.

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"Shall not be infringed"