See #32.
That object you heard flying past you wasn’t a complete bullet; it was a piece of jacket. They’re noisy because they’re irregularly shaped and spinning rapidly.
I still wouldn't want to get hit by it. Thank you for the clarification.
Wait. Wait. Wait! The example you posted was of a guy blasting directly into a steel plate. In such a case, I could understand your explanation; however, as I mentioned, we were shooting plastic targets. I assume whatever flew past me hit a rock, and probably not directly. It would still be noisy, because I'm sure it was spinning and tumbling at that point.