Either you got a bad one or he got a good one.Carried a S&W AR for several years at work. It went bang when you pulled the trigger. That's the nicest thing I can say about it. I'm not a fan at all. Least accurate AR I have ever had. Tried different ammo to no avail. My AR gunsmith went through it and the best he could come up with was the barrel was junk.
I had no choice as it was what we were issued. Hopefully S&W have begun to do a better job.