FIRST, I don't know how much experience you have. I also don't need to know, so don't be offended if you are a long-time shooter and know all this stuff. And, in not knowing, I feel compelled to tell you this: NEVER, EVER put your fingers close to the juncture of the front of the cylinder and the forcing cone (rear of the barrel) where the cylinder and the barrel meet. There is always some blowby there and you can injure yourself if you get your hands up there when firing the gun.
However, there is no reason why you should be getting lead or jacket fragments in your face when you fire the gun. I've been shooting all my life and I've never had ANY of my revolvers do that! And, I've got a few of them, too.
I'll also qualify the above statement by saying that I have always inspected my weapons exceptionally closely before I bought them and I stay away from junk, which category, unfortunately, S&W is starting to slide toward, in my opinion. If you are going to buy S&W, I recommend you buy an old, 1970's or earlier revolver in good to excellent condition and not the newer ones. Right out of the box at the gun shop you can see defects in them. There's too many good used ones out there to have to settle for a new S&W with the quality problems they are having. It's really sad.
I would personally contact S&W, (don't be meek or they'll blow you off), complain loudly and demand they take the gun and fix it so that the problem you are experiencing does not happen. Demand they test fire the gun numerous times before they return it to you. You can simply package the gun well, insure it fully and send it to them via UPS; it is legal. ASK THEM TO send you a UPS call tag so they pick up the cost. They may or may not. ALSO, don't even BEGIN to suggest what you think might be wrong with the gun; just give them a full description of the symptoms.